Focus on materials, semiconductors, vacuum, and cryogenics

An atomic layer deposition process for moving flexible substrates

The authors developed a high throughput (70 Å/min) and scalable space-divided atomic layer deposition (ALD) system for thin film encapsulation (TFE) of flexible organic light-emitting diode (OLED) displays at low temperatures (<100 °C). In this paper, the authors report the excellent moisture barrier properties of Al2O3 films deposited on 2G glass substrates of an industrially relevant size (370 × 470 mm2) using the newly developed ALD system. This new ALD system reduced the ALD cycle time to less than 1 s. A growth rate of 0.9 Å/cycle was achieved using trimethylaluminum as an Al source and O3 as an O reactant. The morphological features and step coverage of the Al2O3 films were investigated using field emission scanning electron microscopy. The chemical composition was analyzed using Auger electron spectroscopy. These deposited Al2O3 films demonstrated a good optical transmittance higher than 95% in the visible region based on the ultraviolet visible spectrometer measurements. Water vapor transmission rate lower than the detection limit of the MOCON test (less than 3.0 × 10−3 g/m2 day) were obtained for the flexible substrates. Based on these results, Al2O3 deposited using our new high-throughput and scalable spatial ALD is considered a good candidate for preparation of TFE films of flexible OLEDs.

In this paper, energy and exergy analyses of atomic layer deposition (ALD) of Al2O3 nano-film has been conducted. First, based on the first law of thermodynamics, the energy flow in ALD of Al2O3 nano-film preparation system is analysed. Second, the exergy flow in the system is analysed based on the second law of thermodynamics. Two different kinds of exergy efficiencies are introduced, including the simplest definition for exergy efficiency and the degree of perfection. In the end, the exergy efficiency in this system is calculated by using the two kinds of exergy efficiency calculation methods. The results of analyses on the ALD of the Al2O3 nano-film process demonstrate the extremely low efficiency of energy in the ALD system. Thus, it is necessary and meaningful to find ways to reduce energy consumption and improve the energy utilisation efficiency in ALD operation process.

Surface chemistry and film growth during TiN atomic layer deposition using TDMAT and NH 3

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

Thin film atomic layer deposition equipment for semiconductor processing

Modeling and simulation softwareSection:ChooseTop of pageModeling and simulation s... <<Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s...Comsol has released version 5.1 of its Multiphysics software, which allows users to create models, build simulation apps, and share the apps via the Comsol server mode. Upgrades include full integration between the model builder and the application builder. Users can easily switch between them and update the model and the app simultaneously. The model builder’s functions and features can be used in the application builder with no need to interface between the software packages. Both models and apps can be saved in the unified .mph file format. Version 5.1 simplifies code generation and provides many template codes for users who want to implement highly customized commands and operations. Additions have also been made to add-on products that expand the simulation platform for electrical, mechanical, fluid flow, and chemical applications. Comsol Inc, 1 New England Executive Park, Burlington, MA 01803, http://www.comsol.comMagnetocaloric effect measurement softwareSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea... <<Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s...A software analysis program from Lake Shore Cryotronics allows users in the magnetic research field to characterize and determine the nature of magnetic phase transitions in magnetocaloric effect (MCE) candidate materials. It is offered in a free beta trial version for users of Lake Shore’s 7400 or 7300 series vibrating sample magnetometers (VSMs). According to the company, the software simplifies the process of calculating MCEs and makes it easier to prepare the measuring protocol. The program imports measured isothermal M(H) and isofield M(T) magnetization curves recorded using Lake Shore VSM system data acquisition software. It uses those data to calculate the materials’ refrigerant capacity and their magnetic entropy change from peak value and full width at half maximum. Lake Shore Cryotronics Inc, 575 McCorkle Boulevard, Westerville, OH 43082, http://www.lakeshore.comSemiconductor processing failure analysisSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ... <<Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s...Park Systems has released the NX-Hivac atomic force microscope system for research and industrial failure analysis in highly doped semiconductor processing. It uses high-vacuum scanning spreading resistance microscopy to enable higher sensitivity and resolution than can be achieved in ambient conditions. The applied force between tip and sample under ambient or dry nitrogen conditions is four times higher than in a vacuum; the lower force under vacuum reduces the strain in thin films of target samples, which results in higher spatial resolution and longer tip life. The NX-Hivac can load up to five samples and measure a seven-decade dynamic range of dopant concentration. It has a closed-loop XY scanner for accurate zoom-in imaging and a low noise ratio of 0.30 Å. Motorized laser alignment and high-resolution axis optics enhance ease of use. Park Systems Inc, 3040 Olcott Street, Santa Clara, CA 95054, http://www.parkafm.comComputing and modeling softwareSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so... <<Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s...MathWorks has released version 2015a of its Matlab mathematical computing software and Simulink graphical environment for simulation and model-based design. Enhancements include new graphical controls and displays and antenna-to-bits simulation and testing of wireless communications and radar systems. It also has four new products: an antenna toolbox for designing, analyzing, and visualizing antenna elements and arrays; a robotics system toolbox for designing and testing algorithms for robotics applications; a Simulink test for creating test harnesses, authoring complex test sequences, and managing simulation-based tests; and a vision HDL toolbox with pixel-streaming algorithms for designing and implementing vision systems on field-programmable gate arrays and application-specific integrated circuits for image processing, video, and computer vision systems. The MathWorks Inc, 3 Apple Hill Drive, Natick, MA 01760-2098, http://www.mathworks.comOptical engineering softwareSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw... <<Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s...Photon Engineering has introduced version 14.40 of its optical engineering software, FRED. Used in product development, it merges optical elements with mechanical components to build integrated models. Among its improvements is increased flexibility in the feature that allows objects to be isolated in 3D view, since property-based isolation is now allowed. A new multiple selection method lets users simultaneously assign multiple properties such as coatings, ray-trace controls, and materials to different nodes in an object tree. Keywords, a new property in FRED, can facilitate complex model construction and configuration by acting as pass-throughs for objects assigned to them. A complete list of new FRED 14.40 features can be found in the developer release notes, accessible from the Help menu after installation. Photon Engineering LLC, 310 South Williams Boulevard, Suite 222, Tucson, AZ 85711, http://photonengr.comSemiconductor measurement toolSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement... <<Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s...Craic Technologies has developed its 20/30 XL microspectrophotometer to nondestructively analyze microscopic samples or microscopic areas on large devices, such as small-spot film thickness on 300-mm wafers. The instrument can acquire data by absorbance, reflectance, or luminescence spectroscopy. It can be used for UV-visible or near-IR microscopy and for high-resolution digital imaging of semiconductor and other types of samples. Users can add the company’s Apollo Raman spectroscopy modules to acquire Raman microspectra. Featuring calibrated variable apertures and manual and automated operation, the flexible instrument is designed to attach to large frames that can accommodate large-scale samples. Applications include mapping thin-film thickness of large devices, locating and identifying contaminants, and measuring strain in silicon. Craic Technologies Inc, 948 North Amelia Avenue, San Dimas, CA 91773, http://www.microspectra.comAutomated wafer-level device characterizationSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev... <<Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s...Keysight Technologies has unveiled WaferPro Express 2015, a software platform for high-volume measurement of wafer-level devices and circuit components for R&D applications such as device modeling, process monitoring, and component characterization. By controlling all components—instruments and wafer probers alike—WaferPro Express reduces setup complexity and provides a unified platform for efficient automated measurement and data management. It is integrated with Cascade Microtech’s Velox 2.0 probe station control software, a combination which allows for complete wafer-map synchronization. That enables easy, error-free information exchange between the software, including wafer alignment, sites, and die information. To maximize efficiency during RF measurement, WaferPro Express periodically monitors the stability of the RF calibration. Keysight Technologies Inc, 1400 Fountaingrove Parkway, Santa Rosa, CA 95403-1738, http://www.keysight.comIntegrated circuit patterning metrologySection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter... <<Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s...The Archer 500LCM and SpectraFilm LD10, two advanced metrology systems from KLA-Tencor Corp, support the development and production of integrated circuit devices that are 16 nm and smaller. They are part of the company’s 5D patterning control solution that characterizes and monitors fab-wide processes. The Archer 500LCM system provides accurate overlay error feedback through all stages of the yield ramp, so chipmakers can resolve overlay issues associated with novel patterning techniques such as multipatterning and spacer pitch splitting. Through reliable, precise measurement of film thickness and stress, the SpectraFilm LD10 enables qualification and monitoring of the films and film stacks used in fabrication of FinFETs, 3D NAND, and other devices. KLA-Tencor Corporation, 1 Technology Drive, Milpitas, CA 95035, http://www.kla-tencor.comFluorescence imaging analysis softwareSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal... <<Optical imaging and spect...Solder paste technologyAtomic layer deposition s...PicoQuant has released version 2.0 of its SymPhoTime 64 fluorescence-lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS) software package. It provides new features for time-resolved data acquisition and analysis and for superresolution. They include global analysis of FCS and time-correlated single-photon counting (TCSPC) curve fitting, which improve cell measurements, and stimulated emission depletion data acquisition and analysis procedures, such as gated STED. An extended TCSPC binning functionality permits faster analysis and binary export of FLIM images. A newly developed fast pattern-matching approach allows two species to be separated by lifetime and absorption and emission spectra, thereby refining FLIM image analysis. PicoQuant, Rudower Chaussee 29, 12489 Berlin, Germany, http://www.picoquant.comOptical imaging and spectroscopy softwareSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect... <<Solder paste technologyAtomic layer deposition s...Advancements in LightField version 5.0, an upgrade of Princeton Instruments’ scientific imaging and spectroscopy software, include a math engine for analyzing 64-bit data in real time, an interactive virtual optical bench for managing multiple experiment setups, and automatic export of data in various formats. LightField supports the latest Princeton Instruments hardware, including IntelliCal spectral-calibration light sources. When paired with LightField’s automated point- by-point wavelength and intensity calibration, IntelliCal improves wavelength accuracy and NIST-traceable, instrument-independent intensity data by a factor of 10. For time-resolved imaging and spectroscopy applications, LightField provides users with an intuitive oscilloscope-like timing interface to PI-MAX4 ICCD cameras for easy synchronization and gating controls. Princeton Instruments, 3660 Quakerbridge Road, Trenton, NJ 08619, http://www.princetoninstruments.comSolder paste technologySection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technology <<Atomic layer deposition s...Indium Corporation offers its BiAgX solder paste as a drop-in replacement for the high-lead solders used in many high-reliability die-attach and electronics assembly applications. Made with the company’s high-melting solder paste technology, it can survive both high-temperature environments in excess of 175 °C with little degradation of the mechanical structure or other properties and J-STD-020 moisture sensitivity level reflow profiles up to 260 °C in the final solder joint. It does not contain lead, antimony, or specialty materials such as nanosilver or sintering aids. BiAgX reflows, solders, wets, and solidifies like any other solder paste. Available in both dispense and printing forms, it is suitable for small, low-voltage quad-flat no-lead packages used in portable electronics, automotive electronics, and industrial applications. Indium Corporation, 34 Robinson Road, Clinton, NY 13323, http://www.indium.comAtomic layer deposition systemSection:ChooseTop of pageModeling and simulation s...Magnetocaloric effect mea...Semiconductor processing ...Computing and modeling so...Optical engineering softw...Semiconductor measurement...Automated wafer-level dev...Integrated circuit patter...Fluorescence imaging anal...Optical imaging and spect...Solder paste technologyAtomic layer deposition s... <<The Savannah G2 atomic layer deposition (ALD) system from Ultratech Cambridge NanoTech incorporates advanced field-upgradable options that help researchers expand and characterize their portfolio of ALD films. One option is a low-vapor precursor delivery system that enables the growth of novel materials, including single- and multicomponent films from perovskite, yttrium, lithium, and the rare-earth families. Others include ellipsometry, quartz crystal microbalance, and mass spectrometry, which allow for the simultaneous growth of ALD films and the real-time characterization of the deposition process, important capabilities for thin-film R&D. Ultratech Cambridge NanoTech, 130 Turner Street, Building 2, Waltham, MA 02453, http://www.ultratech.com© 2015 American Institute of Physics.

The nearly unmatched conformality of Atomic Layer Deposition (ALD) renders it a powerful deposition technique for applications such as catalysis where high surface areas are critical, or for protective coatings on complex 3D surfaces such as powders or porous materials. In the last decade, ALD for energy storage has come into view. Advances in technology have pushed the requirements of energy storage devices, leading to novel lithium-ion battery (LIB) concepts such as 3D-structured electrodes, thin-film electrode and the combination of both. These concepts enable high-power and high-energy integrateable batteries, but require a conformal deposition technique for the current collectors, electrodes, solid electrolytes and interfacial coatings alike. Besides 3D structuring, materials design of the LIB electrodes is paramount to achieve higher power and higher energy densities, beyond traditional electrode materials such as LiCoO2, and LiMnO2which are limited to volumetric capacities of 550-700mAh/cm³. Traditionally, the main focus of materials development for batteries has been on crystalline compounds. However, several indications exist that higher energy and power density can be found in amorphous materials. ALD is not only excellently suited to deposit conformal films, but also able to grow high-quality amorphous films at low deposition temperatures, enabling the study of amorphous thin-film electrodes. In this work, ALD of vanadium oxides for applications as lithium-ion electrodes is envisioned. Vanadium oxides were amongst the first materials to be studied as LIB cathodes, but were never commercialised. V2O5 is a well-known LIB electrode, but the rather low volumetric energy density (when storing one lithium) or poor cyclability (when storing 2-3 lithium ions) have prevented its large-scale commercialisation in the past. Here, we demonstrate the ALD deposition of amorphous and crystalline V2O5, and two ‘flavours’ of amorphous VO2, from a single vanadium precursor (Tetrakis[ethylmethylamino] vanadium). We demonstrate the crystallisation of these films into crystalline films in the Wadsley series, and are able to unravel the influence of initial ALD process, atmosphere, temperature and substrate on the crystallization and oxidation of the VO2 films. With this in mind, we are able to obtain phase-pure crystalline vanadium oxides in the whole Wadsley series (VO2–V6O13–V4O9–V3O7–V2O5), which show very high energy densities up to more than double that of typical bulk cathodes (1380mAh/cm³ for V4O9). The amorphous initial states (amorphous VO2 and V2O5) are often not considered due to their lack of a clearly defined electrode potential. However, building on the nature of ALD to grow high-purity amorphous films, these were also investigated here. It was found that, besides also having very high capacities, their kinetics are excellent. Finally, the best candidates were examined on an ALD Pt-coated silicon micropillar array as 3D-structured thin-film electrodes. The 20x surface enhancement of the micropillar substrate enhanced the footprint capacity of the 40nm films from approximately 2-5µAh/cm² to 40-100µAh/cm², with the highest capacity for amorphous VO2(>100µAh/cm² for the 40nm film), while at the same time maintaining the excellent thin-film kinetics of the planar films, in effect simultaneously demonstrating the potential of ALD to deposit 3D thin-film electrodes as well as a tool to study amorphous and crystalline films. In conclusion, a wide range of crystalline and amorphous vanadium oxides were demonstrated from a single vanadium-precursor based ALD process. All films were examined as potential lithium-ion battery electrodes, and showed promise of very high volumetric capacities. In particular, the amorphous films and the crystalline VO2 (B) not only displayed very high capacities, but also excellent kinetics, enabling both high-energy and high-power electrodes. Figure 1

Uniform tantalum oxide thin films, with a growth rate of 0.6 Å/cycle, were fabricated on vertically aligned, 10 cm-long, silicon substrates using an innovative atomic layer deposition (ALD) design. The ALD system, with a reaction chamber depth of 13.3 cm and 18 vertical enclosed channels (inner diameter 1.3 cm), was coupled with a shower-head type precursor conduit plate bearing 6 radial channels. This design enabled deposition on 6 silicon substrates at a time. The degrees of non-uniformity of deposits along the length of the silicon wafer and across different positions in the ALD chamber were found to be 1.77%-6.21% and 3.27%-5.45%, respectively. A further advantage of the design is that the conduit plate may be modified and the number of channels increased to process 18 substrates simultaneously, thus moving toward efficient and expedited ALD systems.

Atomic layer deposition (ALD) can synthesize materials with atomic-scale precision. The ability to tune the material composition, film thickness with excellent conformality, low-temperature processing, and in-situ real-time monitoring makes this technique very appealing for a wide range of applications. In this contribution, we will show that ALD is already widely used in the manufacturing of industrial silicon solar cells, where ALD aluminum oxide is used for the passivation of the rear of PERC (Passivated Emitter and Rear Contact) solar cells. ALD aluminum oxide layers can also be used to reduce the contact resistance and firing temperature for phosphorous diffused surfaces. We will show that ALD layers can also avoid potential induced degradation (PID, a possible failure mode for large photovoltaic systems) at the solar cell level. ALD capping layers can also be used to reduce light and elevated temperature induced degradation (LeTID), which is a recently identified failure mode for high-efficiency solar cells, by acting as a blocking layer for hydrogen. Finally, we will show that ALD layers are enabling world-record CZTS (copper-zinc-tin-sulphide) solar cells.

Nanocoating individual cohesive boron nitride particles in a fluidized bed by ALD

Atomic layer deposition (ALD) processes for the growth of ZrO2 and TiO2 were developed using novel precursors. The novel processes were based on cycloheptatrienyl (CHT, -C7H7) – cyclopentadienyl (Cp, -C5H5) compounds of Zr and Ti, offering improved thermal stability and purity of the deposited oxide films. The CpMeZrCHT/O3 ALD process yielded high growth rate (0.7–0.8 Å/cycle) over a wide growth temperature range (300–450 °C) and diminutive impurity levels in the deposited polycrystalline films. Growth temperatures exceeding 400 °C caused partial decomposition of the precursor. Low capacitance equivalent thickness (0.8 nm) with low leakage current density was achieved. In the case of Ti, the novel precursor, namely CpTiCHT, together with ozone as the oxygen source yielded films with low impurity levels and a strong tendency to form the desired rutile phase upon annealing at rather low temperatures. In addition, the thermal stability of the CpTiCHT precursor is higher compared to the usually applied ALD precursors of Ti. The introduction of this new ALD precursor family offers a basis for further improving the ALD processes of group 4 oxide containing thin films for a wide range of applications.

In this work, we fabricated charge-trapping MemTransistors (CTMTs) on a germanium (Ge) substrate with a single-charge-trapping-layer gate-stack or a double-charge-trapping-layer gate-stack. We first constructed the energy band diagram of two gate stacks using transmission electron microscope (TEM) images and by X-ray photoelectron spectroscopy analysis. We deposited Al2O3 as a tunneling layer and a barrier layer using an atomic layer deposition (ALD) system while depositing HfO2 by ALD as the charge-trapping layer whose conduction band offset with respect to Al2O3 is 1.74 eV. Next, we demonstrated the memory characteristics of the CTMTs. By implementing the double-charge-trapping-layer gate-stack on the CTMT, we were able to enlarge the memory windows by 372 mV, improve the retention by 2.7%, and reduce the read disturbance. Furthermore, we demonstrated the synaptic device characteristics of the CTMTs. With the optimization of pulse schemes, we reduced the nonlinearity of potentiation ($\alpha _{\text {p}}$ ) and depression ($\alpha _{\text {d}}$ ) from 8.62 and -6.01 to 0.71 and 0.01, respectively, enlarged the ON/OFF ratio from 10.2 to 66.2, and increased the recognition accuracy from 24.5% to 82.1% simultaneously. With the implementation of the double-charge-trapping-layer gate-stack, we could further enlarge the ON/OFF ratio to 75.3 and increase the recognition accuracy to 86.5% simultaneously.

Recently promising advances have been achieved with phononic crystal (PnC) nanostructures in thermoelectric materials, because the thermal conductivity of PnC samples is lower compared to non-patterned thermoelectric samples due to phonon-boundary scattering. In this study we report on the successful synthesis of PbTe and PbSe thermoelectric layers on patterned porous silicon substrates by a thermal ALD system. PbTe/PbSe nanolaminates grown on porous silicon membranes have higher Seebeck coefficients than the ones grown on regular planar silicon wafers. The higher Seebeck values result from the lower thermal conductivity k in porous structures, which in turn lead to a higher figure of merit ZT. We demonstrate the feasibility to enhance the figure of merit ZT further by modulating the size and periodicity of the pattern and the thickness of the thermoelectric film in relation to the mean free path (MFP) of the phonons of the thermoelectric material. In our study PbTe and PbSe thin films and nanolaminates were synthesized by Atomic Layer Deposition (ALD) technology on regular planar silicon wafers and on macro-porous silicon templates. ALD is a surface saturating, self-limiting, absolutely conformal thin film synthesis technique reacting two pulsed precursors that enable film growth of one atomic layer per growth cycle. Lead bis(2,2,6,6-tetramethyl-3,5-heptanedionato) (Pb(C11H19O2)2), (trimethylsilyl) telluride ((Me3Si)2Te) and (trimethylsilyl) selenide ((Me3Si)2Se) were employed as the chemical ALD precursors for lead, tellurium and selenium, respectively. The surface morphology observations indicate Volmer–Weber growth mechanism of PbTe/PbSe nanolaminates during the thermal ALD deposition process rather than classic layer-by-layer growth. The ALD PbTe/PbSe nanolaminates exhibited complete surface coverage on planar bulk silicon wafers and also inside the pores of microporous silicon membranes. For the case of porous Si templates, the Seebeck measurements in both the horizontal and vertical directions revealed significant enhancement in Seebeck coefficients for PbTe/PbSe nanolaminates synthesized inside strictly periodic lithographically defined porous silicon membranes.

Ternary and amorphous tungsten silicon nitride (W–Si–N) thin films were grown by atomic layer deposition (ALD) using a sequential supply of a new fluorine-free, silylamide-based W metallorganic precursor, bis(tert-butylimido)bis(bis(trimethylsilylamido))tungsten(VI) [W(NtBu)2{N(SiMe3)2}2], and H2 plasma at a substrate temperature of 300 °C. Here, W(NtBu)2{N(SiMe3)2}2 was prepared through a metathesis reaction of W(NtBu)2Cl2(py)2 (py = pyridine) with 2 equiv of LiN(SiMe3)2 [Li(btsa)]. The newly proposed ALD system exhibited typical ALD characteristics, such as self-limited film growth and linear dependency of the film growth on the number of ALD cycles, and showed a high growth rate of 0.072 nm/cycle on a thermally grown SiO2 substrate with a nearly zero incubation cycle. Such ideal ALD growth characteristics enabled excellent step coverage of ALD-grown W–Si–N film, ∼100%, onto nanotrenches with a width of 25 nm and an aspect ratio ∼4.5. Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy analysis confirmed that the incorporated Si and W were mostly bonded to N, as in Si–N and W–N chemical bonds. The film kept its amorphous nature until annealing at 800 °C, and crystallization happened at local areas after annealing at a very high temperature of 900 °C. An ultrathin (only ∼4 nm thick) ALD-grown W–Si–N film effectively prevented diffusion of Cu into Si after annealing at a temperature up to 600 °C.