Hole-Dominated Altermagnetic RuO2 Thin Films Prepared by Reactive Sputtering

Ruthenium dioxide (RuO2) films are studied for use as a bottom electrode of the (Ba, Sr)TiO3 thin-film capacitor. RuO2 films have been deposited by reactive DC magnetron sputtering of ruthenium at a relatively low sputtering power. Stoichiometric RuO2 films are obtained at oxygen partial pressures as low as 0.6 mTorr. The properties of the films have been investigated using techniques such as Rutherford backscattering spectrometry, Auger electron spectrometry, X-ray diffraction, and scanning electron microscopy. The oxygen composition in as-deposited RuOx films increases from 2.0 to 2.4 with the increase of initial O2 partial pressure from 1.2 to 5.6 mTorr at a sputtering power of 200 W. The films deposited under low oxygen partial pressures followed by annealing show preferential crystal growth in the [110] direction, whereas those deposited in high oxygen partial pressures show growth in the [101] direction. A resistivity of 65 µΩ·cm is obtained after annealing at 800°C. Even after high-temperature deposition and subsequent annealing processes, clear interfaces between (Ba, Sr)TiO3 and RuO2 films are obtained.

Using reactive radio-frequency magnetron sputtering, ZnO films with strong c-axi s orientation have been deposited on Si (100) substrates at temperatures ranging from room temperature (RT) to 750℃. We have studied the influence of growth te mperature on the structural characteristics of the as-deposited films in morphol ogy, grain size, microstructure, and residual stress by using atomic force micro scopy, transmission electron microscopy, X-ray diffraction, and Raman spectrosco py. With the measurement of the transmission spectra and photoluminescence (PL) properties, the relationship between the crystallinity and optical properties of ZnO films have been discussed. It is found that the grain size increases with t emperature up to 500℃, and then decreases at 750℃. ZnO grains have an epitaxia l relationship with Si (100) substrate for the films deposited at the temperatur es ranging from RT to 750℃. The films deposited below 500℃ are in the states o f compressive strain while the film deposited at 750℃ is in tensile. The differ ence in growth temperature results in the variation of refractive index, extinct ion coefficient, optical energy gap, and PL properties of the films. It is concl uded that growth temperature dominates the PL behavior of ZnO films. We also dis cuss the physical mechanism affecting the PL behavior.

Characterization of RuO 2 films prepared by rf reactive magnetron sputtering

Graded refractive index layer systems for antireflective coatings and rugate filters deposited by reactive pulse magnetron sputtering

Ion-energy distributions from copper, indium, and tungsten targets were measured during reactive sputtering in argon-hydrogen sulfide (H2S) mixtures, since reactive magnetron sputtering of sulfides from metallic targets is of increasing interest, especially for photovoltaic applications (buffer and absorber layers, i.e., CuInS2, In2S3, or WS2). The mass spectra of the ions show a wide range of molecules HxSn derived from H2S by plasma-assisted attachment both for positive (n≤9) and for negative (n≤6) ions. From the copper and the indium targets metallic ions (Cu+, In+) could be detected. While tungsten and indium sulfur compounds were found, copper does not form compounds with sulfur, caused by its lower chemical reactivity. Positive (Ar+, S+, W+, Cu+, In+, etc.) as well as negative ions (S−, InS−, WS3−) were measured for dc and rf (27 MHz) plasma excitations. The positive ions originate mainly from the plasma in front of the substrate and exhibit energies of about 12 eV for the dc and 18 eV for the rf discharge for the substrate at floating potential. The energy difference is caused by the higher electron temperature in the rf compared to the dc discharge. The ion-energy distributions of negative ions exhibit two distinct peaks. The high-energetic peak can be attributed to ions accelerated in the cathode dark space to a high energy (up to more than 400 eV) corresponding to the cathode (target) voltage. The second peak has its maximum at zero energy decreasing steeply up to energies of about 100 eV. These ions are generated by charge-exchange collisions of energetic species from the target (reflected neutral argon, negative sulfur ions, etc.) on their passage from the target to the substrate caused by the high charge-exchange cross section. rf magnetron sputtering leads to significantly lower energies of negative ions from the target, caused by the lower discharge voltages, which could be advantageous for the deposition of active semiconducting sulfide films.

Currently, tin oxide (SnO2) is a highly sought-after semiconductor material used in perovskite solar cells (PSCs) because of its good transmittance, the appropriate energy level, high electron mobility, high conductivity, ideal band gap and excellent chemical stability. In this study, SnO2 film was successfully prepared by radio frequency reactive magnetron sputtering (RS) under room temperature conditions. The obtained SnO2 thin films not only exhibited high transmittance in the visible region as well as the pure phase, but also had a suitable energy band structure and lower surface roughness than FTO (SnO2:F) glass substrate, which contributes to the improvement of the adjacent interface morphology. The SnO2 films prepared by reactive sputtering could effectively suppress carrier recombination and act as an electron transport layer. Moreover, the maximum efficiency of the device based on reactive sputtering of SnO2 as the electron transport layer (ETL) for planar perovskite solar cells (PSCs) was 14.63%. This study mainly described the preparation of SnO2 by reactive sputtering under room temperature conditions.

Silicon nitride and silicon nitride-based ceramics have several favorable material properties, such as high hardness and good wear resistance, which makes them important materials for the coating industry. This thesis focuses the synthesis of silicon nitride, silicon oxynitride, and silicon carbonitride thin films by reactive magnetron sputtering. The films were characterized based on their chemical composition, chemical bonding structure, and mechanical properties to link the growth conditions to the film properties. Silicon nitride films were synthesized by reactive high power impulse magnetron sputtering (HiPIMS) from a Si target in Ar/N 2 atmospheres, whereas silicon oxynitride films were grown by using nitrous oxide as the reactive gas. Silicon carbonitride was synthesized by two different methods. The first method was using acetylene (C 2 H 2 ) in addition to N 2 in a Si HiPIMS process and the other was co-sputtering of Si and C, using HiPIMS for Si and direct current magnetron sputtering (DCMS) for graphite targets in an Ar/N 2 atmosphere. Langmuir probe measurements were carried out for the silicon nitride and silicon oxynitride processes and positive ion mass spectrometry for the silicon nitride processes to gain further understanding on the plasma conditions during film growth. The target current and voltage waveforms of the reactive HiPIMS processes were evaluated.

Controlling preferential growth of chromium – Nitrogen R-HiPIMS and R-DCMS films by substrate magnetic biasing

Interfacial and optical properties of ZrO2/Si by reactive magnetron sputtering

The stress-temperature behaviors of RuO2 thin films on (100) Si were investigated by measuring the deflection of film-coated substrates in situ during thermal cycling between 25 and 700 °C. The average biaxial elastic modulus [E/(1−ν)] and thermal expansion coefficient (α) of RuO2 thin film were also determined using the stress-temperature curves of the films on both (100) Si and quartz substrates. For this study, RuO2 thin films were deposited by rf magnetron reactive sputtering at the substrate temperature range of 25–450 °C. As-grown thin films deposited between 300 and 450 °C showed different stress-temperature behavior, which was caused mainly by the microstructure of the thin films. The values of [E/(1−ν)]RuO2 and αRuO2 were calculated to 3.09×1011 Pa and 10.47×10−6/°C, respectively, in the range of 350–600 °C. The αRuO2 obtained from the stress data was compared with the α value calculated from the thermal expansion coefficient, αa and αc, of RuO2 single crystal. Both values were found to be in good agreement.

Copper oxide thin films were deposited on glass substrates at various growth temperatures by the reactive radio-frequency magnetron sputtering method. The band gap energy, carrier concentration and figure of merit of the CuO thin films were found to depend significantly on the growth temperature. All of the CuO films, irrespective of growth temperature, showed a monoclinic structure with the main CuO $$\left( {\bar 111} \right)$$ orientation, and the crystallite size, determined by using Scherrer’s formula, was about 50 nm for the thin film deposited at 25 °C. The highest figure of merit occurred for the film grown at 300 °C with an optical transmittance of 62.9% in the wavelength range of 800–1100 nm. The results suggest that the optimum growth temperature for growing high-quality CuO thin films is 300 °C.

Modelling of the hysteresis effect of target voltage in reactive magnetron sputtering process by using neural networks

Growth temperature was found to play a crucial role in determining the structure of stoichiometric TiN films deposited on Si(100) by reactive magnetron sputtering. X-ray diffraction, transmission electron microscopy (TEM), and reflection high-energy electron diffraction were used to show that films deposited at substrate temperatures Ts ranging from 700 to 1100 °C were polycrystalline, with either (100) preferred orientation or mixed (100) and (111) orientations. Films deposited using a two-temperature technique were epitaxial with the relationships TiN(100)//Si(100) and TiN[011]//Si[011] but with considerable misorientation. The most highly oriented films were obtained when 45 nm was first deposited at Ts =750 °C, followed by 250 nm at 1000 °C. High-resolution cross-sectional TEM studies showed that increasing the nucleation temperature above 750 °C led to random orientation of TiN lattice fringes relative to the Si lattice. This was explained by the small energy difference between oriented and misoriented TiN nuclei due to the large lattice mismatch (22%).

Reactive magnetron sputtering in a mixed Ar/CH4 discharge has been used to deposit 3C-SiC films on (111)-oriented Si substrates. The carbon content as well as the crystalline structure was found to depend on both the CH4 and Ar pressures. At a total pressure of 3 mTorr and a CH4 partial pressure of 0.6 mTorr, epitaxial stoichiometric films were obtained at growth temperatures as low as 850 °C. The epitaxial nature of the films was established by x-ray diffraction using a combination of reciprocal space maps, texture scans, and 360° φ scans. Based on these analyses it could also be concluded that double-positioning domains rotated 60° to one another as well as other defects, giving rise to a mosaic broadening in the reciprocal space maps, were present in the films. Furthermore, based on plasma probe measurements and determination of the electron energy distribution functions in the near-substrate vicinity, the low growth temperature of 850 °C is suggested to be a consequence of an effective decomposition of CH4 molecules in the plasma.

In situ scanning tunneling microscopy studies of the evolution of surface morphology and microstructure in epitaxial TiN(001) grown by ultra-high-vacuum reactive magnetron sputtering