Nanostructured Telluride Films on Macroporous Silicon for High Efficiency Thermoelectric Devices

The microstructure and optical properties of alumina and titania multilayer coatings prepared using atomic layer deposition (ALD) has been investigated. The titania layers were prepared using TiCl4+H2O as the precursors while two different precursors, Al(CH3)3+H 2O and AlCl3+H2O, were used to deposit the alumina layers. The results show that ALD can be used to produce amorphous, stoichiometric alumina and titania thin films with uniform thicknesses at low temperatures (120 °C). An antireflective coating design based on 4 alternating layers of titania and alumina was prepared and the resulting reflectance compared to theoretical calculations. The results demonstrate that ALD is a suitable technique for the deposition of optical thin films at temperatures compatible with thermally sensitive substrates.

Due to various applications in electronic and optical fields, considerable efforts have been made to develop ZnO based semiconducting materials. ZnO has a wide and direct band gap of 3.37 eV, large exciton binding energy (60 meV), high mechanical and thermal stabilities, and good electrical conductivity. Therefore, ZnO thin films are intensively investigated and applied in solar cells, piezoelectrical devices, gas and biological sensors, catalysts, and high-efficiency short-wavelength optoelectronic nanodevices. To further enhance the properties of ZnO, researchers have been synthesizing ZnO films doped with aluminum or indium. Al doped ZnO (AZO) thin films have been highly developed featuring non-toxicity, low material cost, good thermal stability, high optical transmittance, and good electrical conductivity. [1, 2, 3] Many techniques have been used to deposit AZO thin films currently, such as sol gel processing, magnetron sputtering, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). Among these film deposition methods, ALD has been extensively investigated for the deposition of thin films of metals, alloys, semiconductors, and oxides. Compared with other techniques, ALD is considered as a novel technique for the deposition of AZO films due to its characteristic feature of self-limiting surface saturating reactions in each ALD cycle. ALD technology consequently and accurately controls the layer thickness with unprecedented atomic level precision, as well as the stoichiometry, composition, uniformity of large areas and maintains excellent conformity over complex surface nanostructures. The other advantage of ALD technology is to introduce each ALD chemical precursor sequentially separated by time to react on the surface of the structure. The concentration of dopant in the ZnO films can be precisely controlled by the number of ALD cycles, so that the physical properties of AZO films, such as carrier density and conductivity, can be adjusted to meet the requirements of different applications. In this study, a Savannah 100 cross-flow thermal ALD reactor was used for the deposition of Al doped ZnO thin films. The precursors of aluminium, zinc and oxygen used in the ALD process for the synthesis of Al doped ZnO thin films were trimethylaluminium (TMA: Al2(CH3)6), diethylzinc (DEZ: (C2H5)2Zn) and DI water. The growth temperature of AZO thin films was maintained at 250 oC. The flow rate of N2, used as a carrier gas, was accurately controlled at 20 sccm. In order to deposit ALD AZO films with various percentages of aluminium, TMA cycles were introduced once in every 30 pulses of DEZ and H2O injection. After deposition, AZO films were annealed in air at 500 oC, 600 oC, and 700 oC for 30 min, respectively. X-ray diffraction (XRD) was performed to characterize the crystal structure of ALD ZnO and AZO films. Field emission scanning electron microscopy (FE-SEM) was used to inspect the morphology of AZO films before and after annealing. The surface roughness was analyzed by atomic force microscopy (AFM). The compositions of AZO thin films were analyzed by energy dispersive X-ray spectroscopy (EDS). The sheet resistivity of AZO films was determined by using four-point probe measurements. Raman spectroscopy and photoluminescence (PL) were used to investigate the properties and detect structures of ALD AZO films. The band gaps of AZO films prepared by the ALD process were analyzed from PL spectroscopy results. The materials property and defect structure of ALD AZO films were investigated by Raman spectroscopy.

Elastomeric primer and adhesive systemSection:ChooseTop of pageElastomeric primer and ad... <<Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Master Bond X21Med is a single-component elastomeric compound that passes ISO 10993-5 tests for cytotoxicity. It was developed as a primer to promote adhesion between polyolefins and other surfaces such as metals, ceramics, composites, and other kinds of plastics, but it can also bond two polyolefin materials. Easy to use, X21Med has a low viscosity of less than 250 cps. It cures at ambient temperatures; with heat, it cures more rapidly. It is serviceable from −51 °C to 93 °C. As a primer, X21Med should be applied in a thin layer to the surface and then the solvent allowed to evaporate. When used as an adhesive, it should be applied to both substrates and then mated. The maximum area of bonding effectiveness is about 1 inch squared. Once cured, the clear- to light-amber-colored product is tough but not rigid. It is a reliable electrical insulator and has a volume resistivity exceeding 1014 ohm-cm. The compound has applications in medical device, aerospace, electronics, specialty OEM, and other fields. It is available in pints, quarts, gallons, and five-gallon containers. Master Bond Inc, 154 Hobart St, Hackensack, NJ 07601, www.masterbond.com Atomic layer deposition plasma-processing systemSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p... <<Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Oxford Instruments has announced the novel FlexAL-2D system for atomic layer deposition (ALD) of 2D transition-metal dichalcogenides for nanodevice applications. The FlexAL-2D system implements plasma-enhanced ALD to synthesize layers of 2D molybdenum disulfide films with tunable morphologies—namely, in-plane and vertically standing nanoscale architectures on CMOS-compatible silicon dioxide and silicon substrates. The wide parameter space offered by the ALD system allows 2D transition-metal dichalcogenides to be grown at lower temperatures than those used in chemical vapor deposition furnaces. With atoms, high temperatures can increase their diffusion on semiconductors and make it harder to place them at the right spot. According to the company, the FlexAL-2D system yields materials of high quality with precise digital thickness control over large-area, 200 mm wafers. Oxford Instruments plc, 300 Baker Ave, Ste 150, Concord, MA 01742, www.oxford-instruments.com Cold cathode vacuum transducerSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans... <<X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES The MKS Granville-Phillips 523 wide-range cold cathode vacuum transducer is suitable for applications that require an economical cold cathode with limited accuracy for simple, repeatable pressure measurement. It combines diverse materials and two types of discharge. The 523 covers a wide pressure range from 10−7 torr to atmosphere without the use of a conventional heat-loss Pirani sensor. A high-pressure discharge cell makes a second vacuum sensor unnecessary. The device can be mounted in any orientation, has a simple analog output, and complies with Restriction of Hazardous Substances and CE standards. Applications include analytical equipment such as mass spectrometers, scanning electron microscopes, industrial coating systems, and general vacuum-based pressure measurement apparatus. MKS Instruments Inc, 2 Tech Dr, Ste 201, Andover, MA 01810, www.mksinst.com X-ray fluorescence systemSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence system <<Precision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Bruker has announced its S8 Tiger Series 2 wavelength dispersive x-ray fluorescence (WDXRF) system for advanced quantitative elemental analysis in academic and industrial research and materials quality control. Measurement times are reduced, sample throughput is increased, and time to result is improved, typically by 25% over the previous model. The S8 Tiger Series 2 features XRF2 small spot mapping for detailed maps of elemental distributions in materials. With a 300 µm spot size, XRF2 offers the highest spatial resolution available in WDXRF, according to Bruker. The system introduces the company’s novel HighSense technology, which offers a wide linear dynamic range to enable higher precision levels for process and quality control. The x-ray optics improves sensitivity and spectral resolution to benefit a wide range of applications, including recognition of foreign particles and analysis of material properties in metals, minerals, semiconductors, glass, ceramics, and nanotechnology. Bruker AXS GmbH, Oestliche Rheinbrueckenstr 49, 76187 Karlsruhe, Germany, www.bruker.com Precision UV mirrorsSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrors <<Solder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Edmund Optics offers its TechSpec precision UV mirrors in deep-UV (DUV) and new vacuum-UV (VUV) enhanced coatings. They are suitable for use in numerous optical setups to reflect UV light, including fluorescence microscopy and spectrometry, and for various commercially available light sources. The mirrors with DUV coating offer excellent reflection from 190 nm to long-wave IR (LWIR), and the VUV-coated mirrors provide optimized reflection from 120 nm to LWIR. Designed for 0° angle of incidence, TechSpec precision UV mirrors exhibit greater than 78% reflectivity at their specified design wavelength. The mirrors are manufactured from a fused silica substrate and feature aluminum-based coatings for low polarization sensitivity. A surface flatness of λ/10 and a surface quality of 10-5provide for maximum precision. Six models are available in 12.5 mm, 25 mm, and 50 mm diameters. Edmund Optics Inc, 101 E Gloucester Pike, Barrington, NJ 08007-1380, www.edmundoptics.com Solder paste for fine-feature printingSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea... <<Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Indium Corp has developed an air and nitrogen reflow, no-clean, lead-free solder paste to meet the fine-feature printing requirements of mobile manufacturers. The Indium11.8HF-SPR (T5-MC) paste is formulated for use with type 5 powder. It delivers high-stencil print-transfer efficiency on a broad range of processes while maintaining high reflow performance, and it is halogen free, per the International Electrochemical Commission’s standard 61249-2-21 test method EN14582. It offers high transfer efficiency through small apertures less than or equal to 0.66 AR and a long stencil life greater than 12 h. Since the paste eliminates hot and cold slump, it inhibits bridging and solder-beading defects. An oxidation barrier avoids the potential for head-in-pillow and graping defects. Indium Corporation, 34 Robinson Rd, Clinton, NY 13323, www.indium.com Process for diamond-like coatingsSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ... <<Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES By incorporating plasma activation, Intlvac has enhanced the reaction kinetics of its diamond-like carbon (DLC) coating machines that use chemical vapor deposition technology. Coupling a dense plasma to carbon‐based precursor gases creates the favorable reaction energetics needed to form diamond-like material, including tantalum carbide ceramic microstructures. Using the company’s new process recipe, the machines produce hard, wear-and-abrasion-resistant DLC coatings to protect substrates, including temperature-sensitive ones, exposed to harsh environments. The smooth coatings are suitable for low-friction applications. They are chemically inert and appropriate for in situ biomedical uses. The standard Intlvac platform can produce DLC thicknesses from several microns to 10 nm on various substrate materials. Those include silicon, germanium, optical glasses, chalcogenides, sapphire, metals, and plastics. Intlvac Thin Film Corporation, 1401 Duff Dr, Unit 600, Fort Collins, CO 80524, www.intlvac.com Liquid transfer pumpSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pump <<New literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES KNF has designed an economical solenoid-driven diaphragm pump for OEM users. The FL 10 pump features a nominal liquid flow rate of 100 mL/min against atmospheric pressure, simple linear flow rate adjustment, and a maintenance-free expected lifetime of 10 000 h. It can be operated to 14.5 psig (1 bar). Spring tension in the linear solenoid drive keeps the flow through the FL 10 tight in both directions when turned off and makes additional check valves unnecessary. Built to operate in demanding environments such as wet or dusty areas, the pump has an IP65 protection rating. Sealing between the pump housing and the linear drive ensures safe operation. In case of a ruptured diaphragm, liquid is kept away from other areas of the system. Chemically resistant flow-path materials in the FL 10 allow for reliable transportation of aggressive media. The company’s novel diaphragm technology transports liquid gently, so its pumps can handle sensitive fluids. KNF Neuberger Inc, 2 Black Forest Rd, Trenton, NJ 08691-1810, www.knfusa.com New literatureSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literature <<Ellipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Vacuum process monitoring brochure Hiden Analytical has released a brochure on its quadrupole mass spectrometers for vacuum process monitoring. Systems cover the full pressure range from UHV for background species and leak detection to the millibar regime for process monitoring and control. The HPR-30 system addresses the higher-pressure regimes. It features integrated dry vacuum pumping and overpressure protection and is configured to mount directly to the process chamber. The 300 amu mass range is applicable to most process environments, with alternative mass range options available for specialized applications. At lower pressures below 5 × 10−3 millibar, the dual-mode Hiden HMT residual gas analyzer (RGA) uses a Faraday detector for high-pressure operation. It works from low pressures to UHV with electron multiplier detection and offers partial pressure detection sensitivity to 2 × 10−13 millibar. The HALO and HAL RGA series operate at lower-pressure regimes with extensive mass range options up to 1000 amu and minimum detectable partial pressures down to 5 × 10−15 millibar. Hiden Analytical Inc, 37699 Schoolcraft Rd, Livonia, MI 48150, www.hideninc.com Ellipsometer for thin-film measurementsSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil... <<Specialized vacuum gauges...CITING ARTICLES According to Horiba Scientific, its Uvisel Plus modular ellipsometer includes a new generation of the FastAcq acquisition technology, which can measure thin-film samples faster and more accurately than previously possible. The technology features new electronic data processing and a high-speed monochromator. Samples from 190 nm to 2100 nm can be measured within 3 min at high resolution. The technology allows for continuous adjustment of the spectral resolution along the measurement range. The Uvisel series phase modulation technology can deliver pure, efficient polarization modulation for accurate and sensitive ellipsometric parameter measurements, such as critical thin transparent layers deposited onto glass substrates. The Uvisel Plus is considered a reference ellipsometer for materials science. It is suitable for thin-film thickness and optical constant measurements in materials research and processing, flat-panel displays, microelectronics, and photovoltaics. Horiba Scientific, 3880 Park Ave, Edison, NJ 08820, www.horiba.com Specialized vacuum gauges and controllersSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges... <<CITING ARTICLES Edwards has released a range of passive gauges and controllers to meet the needs of users with specialized applications in the high-energy physics and UHV fields. The devices are suitable for a wide range of applications, from UHV systems to process industries, and for when an active gauge cannot be used. The passive gauges range from Pirani and Penning gauges to Bayard–Alpert and extractor ion gauge heads. They are used in conjunction with a passive gauge controller to display pressure and serve as an interface. Pressure ranges of 10−9 mbar to 1000 mbar are covered by the PGC201 controller together with Pirani and Penning gauges, and pressure ranges of 10−12 mbar to 1000 mbar are covered by the PGC202 controller together with an integrated Pirani and ion gauge. Edwards, Innovation Dr, Burgess Hill, West Sussex, RH15 9TW, UK, www.edwardsvacuum.com © 2017 American Institute of Physics.

Atomic layer deposition on dental materials: Processing conditions and surface functionalization to improve physical, chemical, and clinical properties - A review

Iridium (Ir) thin films have been extensively investigated for a variety of applications. Ir is a potential optical material for Fresnel zone X-ray microchannel plates, and inductive grid filters. It is also a noble metal making it well suited to corrosion resistance in harsh environments Atomic Layer Deposition (ALD) is considered a special case of chemical vapor deposition (CVD) in that two different chemical precursor materials are alternately introduced into a vacuum chamber where a chemical reaction occurs on the surface of the substrate. This method of thin film growth is self-limiting and conformal and consequently results in precise layer thickness control, stoichiometry, composition, and uniformity across a large surface area. Advantages that are unique to ALD include the ability to grow conformal thin films across complex geometries, and the relatively low temperatures required to achieve film growth. In this work, iridium metal films were synthesized on silicon (Si) and Monel K-500 alloy substrates by ALD using Iridium (III) acetylacetonate known as Ir(acac)3 or [CH3COCH=C(O-)CH3]3 Ir as precursor 1, and industrial grade O2 as oxidizing reactant. The solid Ir precursor was heated to 150 °C, and the substrate temperature was varied to establish an optimum growth window. The lowest temperature in which Ir growth was found is 200 °C, and the thin film growth rate increased as a function of temperature up to 250 °C. Higher temperatures have not yet been attempted due to equipment constraints. The Monel K-500 steel alloy flat discs were cut from commercially available Monel K-500 bars of ~1 inch diameter. In this study we report on the successful synthesis of Ir films on Si and Monel K-500 substrates. Detailed characterization has been performed using X-ray diffraction (XRD) techniques, atomic force microscopy (AFM), and field emission scanning electron microscopy (FE-SEM) of samples which have been notched with focused ion beam (FIB) techniques for cross-sectional film thickness measurements as revealed in Figure 1. The polycrystalline ALD Iridium film exhibited good chemisorption and adhesion to native oxide covered Si substrates, with hydroxyl surface termination. However even with the absence of a SiO2 surface film, the ALD synthesis of Iridium metal films worked equally well on the Monel K-500 steel alloy flat disc substrates and yielded excellent surface coverage.

We report on the development of atomic layer deposition (ALD) processes for integrating optical filter coatings directly onto back-illuminated silicon sensors for ultraviolet applications. These devices, including CCD imaging arrays and large-area avalanche photodiodes, are modified with a two-dimensional doping method utilizing molecular beam epitaxy to provide high internal quantum efficiency in the UV. Detector integrated coatings are then required to recover additional external losses due to natural silicon reflectance at these short wavelengths. This includes the development of broadband AR coatings, multilayer narrowband coatings, and metal-dielectric filters for solar-blind devices. The use of ALD is attractive for this purpose because the low deposition temperature and thermal surface reactions do not degrade the 2D doping layers, and therefore do not result in reduced detector quantum efficiency. Applications implementing these coated detectors related to terrestrial and space astronomy, astrophysics missions, and particle physics experiments will be discussed. Cosmology is experiencing a very exciting time in exploration. Communities of scientists and technology innovators are studying four concepts for flagship future missions selected and supported by NASA. Two of these four missions are Earth-orbiting large aperture telescope observatories that will include UV capabilities. Currently, these ongoing studies have identified high efficiency detectors and high reflectivity mirror coatings as high priority technologies, particularly those that can extend and enhance system performance for UV wavelengths shorter than those previously explored by missions like the Hubble Space Telescope. At wavelengths below 200 nm, typical ALD dielectric oxide materials like TiO2, HfO2, SiO2, and Al2O3 exhibit large optical losses; we have pursued the development of new processes for ALD metal fluorides to extend coating performance into this far UV wavelength range. Thin films of MgF2, AlF3, and LiF are demonstrated using anhydrous hydrogen fluoride (HF) as the fluorine-containing precursor. This is in contrast to alternate ALD methods for fluoride materials which often utilize reactive metal fluorides as the fluorine precursors, and can result in thin films with components of residual metal oxide contamination. The use of HF has allowed for films with good UV optical properties at deposition temperatures as low 100 °C. This enables compatibility with a variety of 2D-doped silicon sensor formats as well as optical components like polymeric diffraction gratings. The deposition rate of these fluoride materials has a more significant substrate temperature dependence than other common ALD chemistries that often display a ‘window’ of uniform film growth per ALD cycle. Characterization of these coatings is performed with measurements of far UV reflectance and transmittance, x-ray photoelectron spectroscopy, x-ray diffraction, ellipsometry, and atomic force microscopy. These ALD fluoride materials are also effective protective coatings for reflective aluminum optics. Protected UV Al mirrors with ALD AlF3 overcoats are shown to be competitive with state-of-the-art commercial mirrors made with conventional physical vapor deposition (PVD) methods. The use of ALD in these components holds promise in reducing the thickness of the overcoat relative to PVD approaches. This has significant performance implications for far UV mirrors and the ultimate short wavelength cutoff of Al mirrors for potential future NASA astrophysics missions. The large scale coating uniformity, and corresponding reflectance uniformity of ALD overcoats is also attractive for the same applications. Additionally, the use of HF-based ALD chemistries can also allow for the thermal atomic layer etching (ALE) of a variety of materials including aluminum oxide. By combining these ALE methods with ALD encapsulation, it is possible to chemically strip the oxidation that occurs on metallic aluminum and effectively replace it with thin fluoride layers. Stable Al mirrors with protective fluoride coatings approximately 3 nm thick are demonstrated with this combined ALE/ALD approach. The environmental stability of these coatings will be described in the context of resistance to high-humidity conditions. Figure 1

All solid-state ion layers has an ever-growing interest in order to accomplish on-chip energy storage devices. As such, lithium-ion synaptic transistor to build artificial neural networks, integrated area-enhanced capacitors and lithium-ion microbatteries for energy supply are suitable candidates fulfilling energy-efficient devices. Atomic layer deposition (ALD) is one of the most promising techniques for manufacturing ultrathin layers for lithium-ion devices with exceptional capabilities to enable conformal growth at atomic scale. In this area, in situ diagnostics has become of vital importance for the growth process understanding especially on view of the air-sensitivity character of lithium ultra-thin layers.The purpose of this work is to present an in situ spectroscopic ellipsometry (SE) study of ALD thin films used on the fabrication of lithium-ion devices. We will consider several aspects of ALD ultrathin films growth, such as film thickness, saturation curves and initial films nucleation. We shall compare in situ SE results with those of ex situ diagnostics such as XRR (x-ray reflectometry) and XPS (x-ray photoelectron spectroscopy).We focus on the characterization of 10-100 nm thin lithium phosphate electrolyte with and without nitrogen doping deposited at ALD temperature range 300-350°C using LiHMDS-TMPO and LiHMDS-DEPA precursors, respectively. On the other hand, the realization of silicon integrated lithium ionic devices requires the implementation of essential barrier films to prevent Li-ion into the Si substrate. We will explore here the ability of titanium nitride depositions to act as lithium-ion diffusion barriers. TiN deposition (10-20 nm thin) by ALD process (350°C-400°C) uses TiCl4 and NH3 precursors.First, we investigate the growth process of LiPO, LiPON and TiN intrinsic layers deposited using thermal ALD. Secondly, we apply in situ and ex situ diagnostics on exemplary LiPO/LiPON deposited on top of the 10 nm ALD TiN film (Figure 1: Monitoring of LiPON thickness vs deposition time using in-situ Ellipsometry). The film thickness deduced from in situ SE measurements was corroborated by thickness measurements with XRR technique (Figure 2: Evolution of LiPON thickness vs ALD cycles using Ellipsometry and SE characterization techniques). Ex situ SE was used most often for WiW uniformity evaluating (Figure 3: 8” Wafer thickness mapping of ALD LiPON layers (a: 10nm TiN film; b: 17nm LiPON film). The preliminary results underline the fact that ALD growth rate and nucleation of lithium electrolyte and titanium nitride obviously depends on the ALD process parameters (temperature, pulse and purge times, number of cycles) but on the substrate nature (silicon, thermal oxide, and metallic). In situ and ex situ diagnostics highlight that initial film growth of lithium electrolytes and TiN layers strongly depends on the precursors kind used in the ALD process and the substrate material employed. Figure 1

Modification of semiconductor surfaces via the growth of metal oxide overlayers, particularly by atomic layer deposition (ALD), has become a topic of recent interest for surface passivation and chemical protection in semiconductor/liquid junctions. For example, in photoelectrochemical water splitting, semiconductor surfaces typically must be protected with insulating or conducting layers that are stable in the electrochemical environment. Further, ALD thin films have been used as overlayers in a variety of other environments including those relevant to batteries, corrosion protection of metals, and for water diffusion barriers. Although thermodynamic stability of a solid phase in various environments can be readily assessed, more complex phenomena such as film hydration and dynamic dissolution/precipitation can occur, dramatically impacting the efficacy of thin protective ALD films. Motivated by this widespread interest in ALD protective layers, we have examined the chemical stability of the two of the most common ALD materials, alumina and titania, in a variety of environments. Films were deposited using thermal ALD using trimethylaluminum and tetrakis dimethylamido titanium for alumina and titania, respectively. Film thickness was then monitored after immersion in various liquid media, which included acidic, neutral and basic aqueous solutions and mercury. Surface morphology was investigated using atomic force microscopy. Our results indicate a drastic increase in stability of the ALD films after post-deposition thermal treatment. Further, for alumina films in pure water, a dramatic restructuring occurs changing film density, thickness, and morphology. Mercury contacts induce a slow increase in film thickness that is attributed to mercury oxide deposition. Finally, we report how the effective surface recombination velocities at these interfaces evolve over the course of thermal annealing and various solution treatments. These results provide important guidelines for the applicability of ALD oxides as protective/passivating films on semiconductor electrodes for applications in sensing and photoelectrochemical water splitting.

We discuss recent research and development efforts towards low cost, size, weight, and power gyroscopes based on piezoelectric MEMS technology. The potential advantages of piezoelectric and ferroelectric material integration into high performance inertial sensors include the following: significantly increased drive amplitudes for Coriolis Vibratory Gyroscopes relative to electrostatic actuators, dynamically equalized and stabilized Quality Factor mismatch (>>10×) in mode-match gyroscopes, and greatly improved drive amplitude (through 3D, sidewall piezoelectric integration) of mode-split gyroscopes. Piezoelectric thin films with large electromechanical coupling coefficients such as lead zirconate titanate (PbZr <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Th <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> , PZT) can help to enable these performance benefits. Specifically, we will discuss efforts to optimize PZT thin film deposition using sputtering and new efforts to deposit 3D, conformal PZT using Atomic Layer Deposition (ALD). ALD is a well-established thin film growth technique that may enable conformal deposition of thin films on high aspect-ratio features. ALD of piezoelectric films on high aspect-ratio features, such as arrayed actuator elements, may improve the areal piezoelectric energy density (the total maximum piezoelectric energy projected onto the area of a planar substrate) by up to 200x or more, yielding proportionally larger drive amplitudes for CVGs compared to planar piezoelectric drive elements. However, ALD processes for piezoelectric films such as PZT or AlN are not widely reported. Recent laboratory demonstrations of ALD processes for PZT and a structural isomorph lead hafnate titanate (PbHf <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Th <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-</inf> <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> , PHT) have been successful, yielding piezoelectric perovskite films following a post-deposition anneal. Here, we present a modified process for ALD PHT which has yielded ferroelectric remanent polarizations (2P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> ) of 68 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , apply the new process to ‘ALL ALD’ PHT film stacks on 3D-MEMS comb structures, and present initial results on the integration of ALD PHT into ‘planar’ MEMS QMG. We will also discuss recent efforts to grow AlN by ALD, which have yielded c-axis oriented polycrystalline films with high dielectric breakdown voltage > 10 MV/cm and e <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31,f</inf> of −0.53 C/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> on platinized substrates. This paper will also present results of applying piezo- and ferroelectric materials to gyroscopes to improve performance including 50% Q-tuning resulting in a>>10x improved quality factor mismatch.

Solid state gas sensors based on semiconducting metal oxides have been widely investigated and utilized in environmental monitoring, chemical process controls and personal safety. In recent years, one dimensional nanostructures, such as nanowires, nanorods, nanotubes and nanobelts, have attracted much attention due to their great potential application in gas sensing, and for overcoming fundamental limitations due to their ultra high surface-to-volume ratio. A variety of methods have been developed to fabricate these nanostructures. The nanostructure based gas sensors demonstrated excellent response and recovery characteristics. However, the developed methods are not convenient for mass production and improvements on sensitivity, selectivity and long term stability are still needed. Atomic layer deposition (ALD) is a film deposition technique based on the sequential use of self-terminating surface reactions. Due to the unique nature of the reaction process, ALD becomes an ideal deposition technique to form atomic thin films and nanolaminate structures. ALD is finding ever more applications for emerging nanodevices. The potential to control thickness at the sub-nm level, and the ability to deposit thin films over highly corrugated substrates with high aspect ratio topography makes ALD of great interest in fabrication of one dimensional nanomaterial. Utilizing fabrication through nanotechnology, ALD has found new opportunities in gas sensors based on metal oxide semiconductors. In this chapter, the general characteristics of atomic layer deposition, the sensing performance enhancements by quasi-1 dimensional nanostructures and nanomaterials, the method to fabricate such nanostructures and the recent exploration of ALD in gas sensing studies are reviewed.

Introduction Single atom catalysts have draw increasing attention of enormous researchers due to its atomically disperation on supports, high efficiency and high catalytic performance. Despite those obvious advantages, there is still rare study about the single atom catalyst’s application in sensors. It was firstly reported the palladium single atoms on TiO2 used as a photocatalytic sensing platform to analyzed organophosphorus pesticide chlorpyrifos[1]. Catalyst-based sensing platform opens up a new pathway for exploring novel strategy of design sensors. Micro-electro-mechanical system (MEMS) process have advantages such as, miniaturization, small size, mechanical parts high resonance frequency, and low power consumption. However, the MEMS prepared by traditional method possess poor stability. Here, we employed the atomic layer deposition to prepare ZnO layer on MEMS. Atomic layer deposition (ALD) is a powerful technique for depositing nanoparticles or thin films and has outstanding advantages, including precise control of size and thickness and excellent uniformity[2], except that the substrate is exposed separately to each gaseous precursor and that the deposition is broken into cycles[3]. ALD functionalized method could gain high performance in thermal stability, mechanical and catalytic performance[4]. It was interesting to obtain single atom MEMS sensors via ALD. Method Prior to ALD, MEMS (Shanghai lingpan Electronic Technology Co., Ltd) were put into ethanol and cleaned by ultrasonic agitation for ten minutes. MEMS were put on quartz wafers and dried in air. ZnO films were deposited onto the MEMS by a hot-wall, closed-chamber ALD reactor. N2 (99.999%) was used as carrier gas. The precursors of ZnO were diethyl zinc and water (H2O). Water acts as an oxidant and enables growth over a wide temperature range. The deposition temperature was 150 °C, and the diethyl zinc was kept at room temperature. After the deposition of ZnO layers, Pt single atoms ALD was subsequently deposited with (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and O3 as precursors at the same temperature as our precious work[2]. Ultimately, the MEMS sensors were tested. Results and Conclusions Fig.1 Response performance for ALD SnO2 layer on MEMS It can be seen from the Fig.1 that sensor response increased with the concentration increase gradually. With the concentration increase for about 1 PPM, response value of sensors gradually reduced. It could also be seen that ALD ZnO sensor have a response time of 90 s and recovery time of 120 s. Baseline with drift less than 4 also demonstrated its good stability. It has little increase in response performance as the concentration increased to 80 PPM, it could be caused by the surface electron transfer arrived balance within high concentrations References [1] X. Ge, P. Zhou, Q. Zhang, Z. Xia, S. Chen, P. Gao, Z. Zhang, L. Gu, S. Guo, Palladium single atoms on TiO2 as a photocatalytic sensing platform for analyzing organophosphorus pesticide chlorpyrifos, Angew Chem Int Ed Engl, (2019).[2] Q. Hu, S. Wang, Z. Gao, Y. Li, Q. Zhang, Q. Xiang, Y. Qin, The precise decoration of Pt nanoparticles with Fe oxide by atomic layer deposition for the selective hydrogenation of cinnamaldehyde, Applied Catalysis B: Environmental, 218 (2017) 591-599.[3] Z. Gao, Y. Qin, Design and Properties of Confined Nanocatalysts by Atomic Layer Deposition, Acc Chem Res, 50 (2017) 2309-2316.[4] M.M. Biener, J. Biener, A. Wichmann, A. Wittstock, T.F. Baumann, M. Baumer, A.V. Hamza, ALD functionalized nanoporous gold: thermal stability, mechanical properties, and catalytic activity, Nano Lett, 11 (2011) 3085-3090. Figure 1

Atomic layer deposition (ALD) of lithium (Li)-based thin films has aroused significant interest in recent years. Promising applications are Li-ion thin-film batteries (TFBs), protective particle coatings, interface model systems, and neuromorphic computing [1,2]. Here, we demonstrate high footprint capacities and excellent high-rate performance of Li4Ti5O12 (LTO) fabricated by ALD for three-dimensional (3D) solid-state TFBs to power upcoming energy-autonomous sensor systems.The simultaneous increase of power and energy density of full-cell 3D TFBs by coating the battery layer stack over microstructured substrates was recently demonstrated [3]. The required conformal, pinhole-free deposition, and stoichiometric control of nanometer-thin films on highly structured surfaces are only accessible via ALD. The vapor-phase technique based on sequential, self-limiting surface reactions is well understood. However, the direct deposition of Li-based anodes remains challenging [1].In previous studies, we developed a thermal three-step ALD process for Li-containing mixed oxides on 200 mm silicon wafers [4, 5]. Lithium-tert-butoxide (LTB) and lithium hexamethyldisilazide (LiHMDS) were proven as suitable precursors, forming high-quality spinel LTO with low impurities after rapid thermal processing. The excellent electrochemical behavior of ALD LTO with LiHMDS was examined and linked to the film texture [5].In this work, we optimize the LTO ALD process with LTB towards high-capacity 3D TFBs and evaluate the electrochemical performance for the first time. A process with tetrakis (dimethylamino) titanium (TDMAT) and H2O at 300 °C was developed, leading to a saturated growth per cycle of 1.06 Å cycle-1 for 7 s LTB pulses. An ALD temperature window between 240 and 320 °C was identified. The effect of the substrate on the initial growth and crystallization behavior was investigated. To overcome the crystallization-inhibiting effect of the titanium nitride current collector, we introduced an ultrathin AlOx interlayer.Planar ALD LTO films with various thicknesses of up to 75 nm were manufactured, increasing the footprint capacity from 1.5 to 4.3 μAh cm-2. We observed a higher surface capacity contribution due to an increased roughness and an inferior C-rate performance with increasing film thickness. 50 nm LTO films demonstrate the optimum energy and power density. A footprint capacity of 1.95 μAh cm-2, corresponding to 67 % of the initial capacity, was achieved at 50 C with an average Coloumb efficiency of 99.9975 %.Next, we evaluate ALD LTO films as 3D TFB anodes for the first time. The conformality of the ALD process on microstructured substrates was improved by extending the LTB pulse and purge times. The purge time is the key factor enabling a step coverage of 70 % for holes with an aspect ratio of 10:1. The 3D samples with an area-enhancement factor (AEF) of 9 coated with 50 nm LTO obtained a footprint capacity of 20.2 μAh cm-2 at 1 C. The significant capacity enhancement of 6.9 compared to planar samples is according to the conformality. The remarkable high-power capability of 3D LTO is demonstrated with 7.75 μAh cm-2 at extreme currents of 5 mA cm-2. A capacity retention of 97.4 % after 500 cycles at 1 mA cm-2 shows the high-rate cyclability. The superior high-rate performance of ALD LTO compared to other 3D anode materials illustrates the enormous potential for realizing high-energy and high-power on-chip 3D TFBs.

Our laboratory is developing new chemical precursors for the growth of electropositive metal and element thin films by atomic layer deposition (ALD). We are also interested in processes that exhibit area selective growth. ALD has many current applications in copper metallization, diffusion barriers, liners, and transistor fabrication. Thermal ALD is often preferred because plasmas can afford low conformal coverage due to radical recombination on the walls of deep and narrow features. There has been extensive progress in the thermal ALD of copper and noble metal films in recent years, because the positive electrochemical potentials allow relatively easy reduction of precursor ions to the metals. Thermal ALD approaches to most other metals and elements in the periodic table are not well developed, due to the negative electrochemical potentials of the ions and a current lack of ALD co-reagents that can convert the ions to the metals or elements. Herein, we will describe the thermal ALD growth of electropositive metals such as nickel, cobalt, aluminium, and others. The ALD of nickel and cobalt metal films has been achieved using precursors containing diazadienyl ligands (precursors 1 and 2). These precursors enable the deposition of cobalt and nickel metal films at temperatures below 200 °C and use alkylamines as benign co-reagents. Growth rates are high (0.60 Å/cycle for nickel, 0.98 Å/cycle for cobalt), high purity, low resistivity metal films are obtained, and the films have low rms roughnesses. The processes exhibit inherent selective growth on metal substrates such as platinum, ruthenium, and copper. By contrast, no growth is observed on insulating substrates. We will also overview a new thermal ALD process for the growth of aluminum metal films. This process entails treatment of surface-bound AlCl3 with a thermally stable, volatile aluminium hydride co-reagent. The growth rate for the aluminium metal ALD process is high, and high purity, low resistivity aluminium metal films are obtained. Prospects for the area selective growth of aluminum metal films will be presented. These examples demonstrate that ALD processes can be enabled for electropositive metals through careful design of precursors and chemistry. Moreover, many of the metal ALD processes exhibit area selective growth. Figure 1

Atomic Layer Deposition (ALD) inherently yields intrinsic, undoped semiconducting films, necessitating the incorporation of controlled impurity levels to convert them into extrinsic semiconductors. While several in-situ doping strategies—such as delta doping during the ALD process—have been explored, post-deposition doping via ion implantation offers superior control over both dose and doping profile. This study examines the effects of Chromium (Cr⁺) ion implantation at 180 keV on the properties of lead chalcogenide (PbTe) thin films, with the goal of enhancing their thermoelectric figure of merit. A fluence of 5 × 10¹⁵ ions/cm² was employed to achieve an estimated Cr doping concentration of 1%. SRIM (Stopping and Range of Ions in Matter) simulations were used to optimize the implantation energy to align the dopant distribution peak with the ALD film thickness.PbTe thin films were synthesized via ALD on silicon substrates with native oxide layers, using lead(II) bis(2,2,6,6-tetramethyl-3,5-heptanedionato) (Pb(C₁₁H₁₉O₂)₂) and (trimethylsilyl) telluride ((Me₃Si)₂Te) as the precursors for lead and tellurium, respectively. Nitrogen served as both the carrier and purge gas. Prior to deposition, substrate surfaces were functionalized to ensure consistent chemisorption of the ALD precursors. The ALD process was conducted over a temperature range of 130°C to 170°C, with precursor delivery temperatures of 170°C for lead and 45°C for tellurium. The deposition chamber was maintained at a base pressure of 500 mTorr.Comprehensive characterization of the PbTe films was carried out before and after ion implantation. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to evaluate film morphology and composition X-ray Diffraction (XRD) analysis confirmed the formation of polycrystalline films with simple cubic structure. Atomic Force Microscopy (AFM) provided detailed information on surface topology, including RMS roughness, grain height, and average grain size. Electrical properties were assessed through temperature-dependent resistivity (ρ(T)), electrical conductivity, Hall mobility, and Seebeck coefficient measurements to evaluate the effects of Cr ion implantation on the thermoelectric performance of the PbTe films.

Atomic layer deposition (ALD) has recently received increasing attention for the growth of high-conformity silicon nitride (SiN) thin films. In particular, plasma enhanced ALD (PEALD) allows SiN deposition at substantially lower temperatures (< 400 °C) with better film properties, compared to thermal ALD. These advantages make PEALD more attractive for ultra large scale integrated circuit (ULSI) device fabrication where the growth of aspect ratio independent and high-quality conformal thin dielectric films is tremendously important. The PEALD of SiN films involves a repetitive two-step process: (1) adsorption and decomposition of silicon-containing precursors and ii) nitridation of the Si-rich surface by active N species emanating from the plasma. Halogenated silanes such as hexachlorodisilane, bis(tertiary-butyl-amino)- silane, and dicholorosilane (DCS, SiH2Cl2) have been utilized as Si precursors. Despite previous studies, the underlying reaction mechanisms of these Si precursors with a N-rich SiN surface during PEALD still remain uncertain. Parameters controlling the rate of growth and uniformity have been demonstrated experimentally, but without knowledge of the reaction mechanisms, direct contributions of specific process conditions cannot be explained. Using first-principles density functional theory (DFT) calculations combined with experimental characterization, we have examined and identified a novel mechanism for the adsorption and decomposition of DCS on a N-rich SiN surface. Our study predicts that the DCS adsorption and dissociation can occur by overcoming a moderate barrier (~ 0.3 eV), far lower than the prohibitively large barriers predicted for previously proposed mechanisms. Through a detailed electronic structure analysis of the reaction intermediates, we have also elucidated the principles underlying the reaction mechanism, notably the hypervalent nature of Si which permits the facile reaction of molecularly adsorbed DCS with primary and secondary amines on the surface, followed by simultaneous Cl release and deportation steps and subsequent HCl formation and desorption. We have examined the same mechanism utilizing alternative precursors and the predicted trends are found to be corroborated with the important properties of the system. Understanding these principles allows us to develop guidelines for processing conditions, such as the importance of maintaining the proper surface composition to facilitate Si precursor adsorption and dissociation. Our study provides insight into the SiN ALD process via chlorosilanes and guidelines to control the deposition for high-quality SiN films and provides a framework for future theoretical studies of surface reactions during ALD.