Cd2SnO4 thin films obtained by d.c. reactive sputtering of Cd-Sn alloys

Cadmium stannate (Cd₂SnO₄) films were prepared by d.c. reactive sputtering from Cd-Sn alloy targets. The electrical and optical properties of these films were found to depend both on the oxygen concentration in the ArO₂ atmosphere during deposition and on the composition of the target. The best figure of merit of about 9.8 × 10^?3ω^?1 was obtained at atomic ratios of 2:1 and 3:1 for Cd:Sn and Ar:O₂ respectively.     

Effects of post-rapid thermal annealing on structural, electrical and optical properties of hydrogenated aluminum doped zinc oxide thin films

In this study, hydrogenated aluminum doped zinc oxide (HAZO) thin films were prepared by DC magnetron sputtering in different H₂/(Ar+H₂) volume ratio atmosphere. The effects of post-rapid thermal annealing (RTA) in Ar+8 % H₂ atmosphere on the structural, optical, and electrical properties of the thin films were investigated systematically. Results showed that the RTA treatment effectively improved the electrical conductivity of the HAZO thin films with small hydrogen content, due to the increase of the Hall mobility and the carrier concentration. The lowest resistivity of the HAZO thin film deposited in 8 % H₂ ratio atmosphere reached 6.3 × 10^?4 Ω cm after RTA. The improved electrical properties of the RTA-treated HAZO films were ascribed to the activation of Al dopants, the increase of oxygen vacancies and the desorption of negative charged oxygen species at the grain. These results implied that RTA process might be useful to fabricate high quality HAZO films with a low thermal budget.     

Electrical properties of glow discharge amorphous SiNx: H thin films

Amorphous SiN_x:H films were prepared by the r.f. glow discharge of SiH₄N₂H₂ mixtures and their electrical properties were investigated as a function of x. Efficient doping is possible in these films and a high photosensitivity as well as a low conductivity of 10^?14 S cm^?1 are obtained by adding B₂H₆ in the molar ratio 10^?4 to SiH₄N₂ in the gas phase. These interesting properties are achieved by the reduction in the hopping conduction due to the incorporation of nitrogen.     

Thin film fabrication of nano-porous 12CaO·7Al2O3 crystal and its conversion into transparent conductive films by light illumination

Thin film fabrication of crystalline 12CaO·7Al₂O₃ (C12A7) with zeolitic structure was examined, and their electrical and optical properties were measured. Polycrystalline thin films were prepared by post-annealing of amorphous films in oxygen atmosphere at temperatures above 800 °C. Choice of substrates was crucial for obtaining single-phase thin films. Although various oxide substrates (single crystals of Al₂O₃, Y-stabilized ZrO₂, MgO and silica glass) were examined, single-phase films were obtained only for MgO substrates and the other substrates reacted with the CaO component in the films during post-annealing. The optical band gap of C12A7 was evaluated to be 5.9 eV. Hydride ions were incorporated into the film by a thermal treatment in a hydrogen atmosphere at 1200 °C. The resulting transparent thin films were converted into transparent persistent electronic conductors exhibiting an electrical conductivity 6.2×10⁻¹ S cm⁻¹ at 300 K by ultraviolet light illumination. This is the first example of transparent conductive thin film in which conductive areas can be patterned directly by light.     

Effect of oxygen partial pressure on the electrical and optical properties of highly (200) oriented p-type Ni<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>O films by DC sputtering

Thin films of NiO (bunsenite) with (200) preferential orientation were synthesized on glass substrates by direct current sputtering technique in Ar+O₂ atmosphere. Nanostructural properties of the NiO films were investigated by X-ray diffraction and also by atomic force microscopic (AFM) studies. Electrical and optical properties of the deposited films were investigated as a function of different partial pressure of oxygen in the sputtering gas mixture during deposition. The films showed p-type electrical conduction and the conductivity depends on the partial pressure of oxygen. The electrical conductivity (σ_RT) was found to be .0615 S cm⁻¹ for films deposited with 100% O₂ and its value sharply decreased with the decrease the partial pressure of O₂; for example σ_RT for 50% O₂ was 6.139 × 10⁻⁵ S cm^-1. The mechanism of the origin of p-type electrical conductivity in the NiO film is discussed from the viewpoint of nickel or oxygen vacancies, which generate holes and electrons respectively. X-ray photoelectron spectroscopic studies supported the above argument. Corresponding optical properties showed that the transparency decreases with increasing oxygen partial pressure and the bandgap also decreases.     

The electrical properties of resistive and dielectric thin films prepared by reactive sputtering from a tantalum-titanium composite target

Resistive thin films of TaTiN and dielectric thin films of TaTiO prepared by reactive co-sputtering in ArN₂ or ArO₂ mixtures from a TaTi composite target were investigated in an effort to extend the data on the electrical properties of films prepared by reactive sputtering from tantalum targets. The composition of the thin films was controlled by changing the ratio of the tantalum area to the titanium area on the composite target surface.For the TaTiN films the resistivity, the temperature coefficient of resistance and the Hall coefficient were investigated as functions of the nitrogen partial pressure and the composition of the films.The dielectric constant, the temperature coefficient of capacitance and tan δ were studied as functions of composition in films of the TaTiO system.The resistivities of TaTiN films sputtered at a nitrogen partial pressure of 4 × 10^?4 Torr varied linearly from 50 to 270 μω cm as the tantalum weight percentage of the films increased from 10 to 90%. The temperature coefficient of resistance for these films decreased, again linearly, from 1000 to ?50 ppm °C^?1 over the same range of tantalum weight percentage.As the titanium weight percentage of the films increased from 10 to 90%, the dielectric constant and tan δ for the TaTiO films varied linearly from 30 to 70 and from 0.008 to 0.025 respectively.It is believed that these resistive and dielectric thin films will be valuable for producing thin film passive elements in hybrid integrated circuits.     

Dependence of the electrical and optical properties of sputter-deposited ZnO:Ga films on the annealing temperature,time, and atmosphere

Effects of annealing process parameters such as annealing temperature, time, and atmosphere on the electrical resistivity and transmittance properties of Ga-doped ZnO (ZnO:Ga) thin films deposited on glass by rf magnetron sputtering were investigated. The electrical resistivity of a ZnO:Ga thin film is effectively decreased with increasing annealing temperature and time in a reducing atmosphere such as N₂ + 5%H₂. This is attributed to passivation of grain boundaries and zinc ions by hydrogen atoms resulting in increases in carrier concentration and mobility. Also the resistivity of 4.9 × 10⁻⁴Ω cm was obtained by annealing at 200°C for 15 h in the same atmosphere, which is not bad for a transparent conductor for solar cell applications. However, annealing at a temperature higher than 400°C is less effective. The lowest resistivity of 2.3 × 10⁻⁴Ω cm was obtained by annealing at 400°C for 1 h in an N₂ + 5%H₂ atmosphere. The optical transmittance of the ZnO:Ga film is improved by annealing regardless of the annealing atmosphere. Annealing in N₂ + 5%H₂ atmosphere widens the optical band gap, while annealing in an O₂ atmosphere makes the band gap narrower, which can be explained as a blue shift phenomenon.     

Growth and vacuum post-annealing effect on the properties of the new absorber CuSbS2 thin films

Post-growth treatments in vacuum atmosphere were performed on CuSbS₂ films prepared by the single-source thermal evaporation method on glass substrates. The films were annealed in vacuum atmosphere for 2 h in temperature range 130-200 °C. The effect of this thermal treatment on the structural, optical and electrical properties of the films was studied. X-ray diffraction (XRD) patterns indicated that the films exhibited an amorphous structure for annealing temperature below 200 °C and a polycrystalline structure with CuSbS₂ principal phase. For the films annealed at temperatures below 200 °C one direct optical transition in range 1.8-2 eV was found. For the films annealed at 200 °C, two optical direct transitions emerged at 1.3 and 1.79 eV corresponding to the CuSbS₂ and Sb₂S₃ values respectively. The electrical measurements showed a conversion from low resistivities (3.10^− 2-9.10^− 2) Ω cm for the samples annealed at temperatures below 200 °C to relatively high resistivities (2 Ω cm) for the samples annealed at 200 °C. In all cases the samples exhibited p-Ztype conductivity.     

Properties of metal-dielectric codeposited films

Optical, electrical, mechanical and corrosion properties have been investigated in the following codeposited metal-dielectric systems: CrSiO₂, CuSiO₂ and (Cu, Zn)SiO₂. The studies were performed in a compositional range of 9–95% Cr, 17–87% Au, 87–99% Cu and 65–85% brass. The films were codeposited in an NRC triode sputtering unit where a variable target aperture was used to control the composition during a single pumpdown. The composite film thicknesses ranged from 200 to 1500 Å. The scratch and corrosion resistance and hardness of the composite films showed considerable improvement over the metal component alone. Marked changes were observed in the reflectance and transmittance spectra with relatively small compositional changes. The data on the optical properties including solar reflectance factors DW (nm) and P%, sheet resistance, scratch and corrosion resistance are presented as a function of composition and thickness of the codeposited films.     

Effects of deposition temperature on structure and properties of mo-doped indium oxide by radio frequency magnetron sputtering

Transparent conductive oxide (TCO) thin films of Mo-doped In₂O₃ (IMO) were prepared on glass substrates by radio frequency magnetron sputtering from the 2 wt% Mo-doped In₂O₃ ceramic target. The depositions were carried out under an oxygen-argon atmosphere by varying the deposition temperature from 200 °C to 350 °C. The crystal structure and thickness of IMO thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of deposition temperature on the electrical and optical transmittance properties of IMO thin films were investigated by four-point probe Hall system and UV-VIS-NIR spectrophotometer separately. The optimum deposited IMO thin films were obtained with resistivity of 6.9 × 10⁻⁴ Ω cm and carrier mobility 45 cm²v⁻¹s⁻¹ at 350 °C. The average optical transmittance of IMO films on glass substrates are over 80% in the near-infrared region.     

Transparent and heat-reflecting indium tin oxide films prepared by reactive electron beam evaporation

Transparent and heat-reflecting indium tin oxide films were prepared by electron beam evaporation of In₂O₃9mol.%SnO₂ in an oxygen atmosphere of about 5×10^?4 Torr. A visible absorption of less than 2%, a thermal IR reflectance exceeding 90% and a d.c. resistivity of approximately 3×10^?4 Ω cm were obtained from films 0.4 μm thick deposited at a substrate temperature of 300°C. Films with similar properties could be prepared with substrate temperatures as low as 150°C.     

Transparent amorphous In-Ga-Zn-O thin film as function of various gas flows for TFT applications

The electrical and optical properties of amorphous indium gallium zinc oxide (a-IGZO) films, which can be used as a channel layer, deposited by radio frequency (rf) magnetron sputtering system at room temperature (RT), were investigated as function of various gas flows. The optical transmittance of films deposited under Ar, O₂ / Ar + O₂ and O₂ / Ar-4% H₂ + O₂ atmospheres in the visible wavelength was consistently above 90% at a wavelength of 550 nm at all gas flows, although the film deposited under Ar-4% H₂ atmosphere exhibited a transmittance of below 50%. The carrier concentration and mobility of the a-IGZO films fabricated under Ar and Ar-4% H₂ were observed slight decrease as a function of the flow, respectively. The thin film transistors (TFTs) with an a-IGZO channel deposited under Ar and Ar-4% H₂ atmosphere exhibited the following good characteristics: V_th of 0.34 V, µ_FE of 3.6 cm² V^− 1 s^− 1, on/off ratio of 10⁶, and S value of 0.04 V decade^− 1.     

SnO2 films prepared by activated reactive evaporation

Transparent conducting films of SnO₂ doped with antimony were prepared on glass substrates by activated reactive evaporation for the first time. The sheet resistance and optical transmittance in the wavelength range 0.4–1.6 μm were studied as functions of various deposition parameters such as the ambient pressure of an 85%Ar15%O₂ mixture, the substrate temperature and the antimony doping concentration in the SnSb alloys. The sheet resistance and optical transmittance showed a strong dependence on the above-mentioned deposition parameters. The best results were obtained for a 90at.%Sn10at.%Sb alloy evaporated in 85%Ar15%O₂ at a partial pressure of about 5 × 10^?4 Torr with a substrate temperature about 350°C. These films, with a sheet resistance of 10 μ/□ had an average transmittance of 95% over the wavelength range 0.4–1.8 μm. The film thickness was about 0.25 μm. Thicker films (about 0.5 μm) had a sheet resistance as low as 1.5 ω/□ with an average transmittance 85% in the wavelength range 0.4–1.6 μm.     

Sputtering of SiO2 in O2Ar atmospheres

The r.f. sputtering of SiO₂ in an ArO₂ atmosphere was studied. The study was carried out to improve the insulating properties of films relative to those produced in a pure argon discharge which showed a clear aging effect on the losses. The O₂ percentage was varied in the range 1%–4% of the total pressure. The improvement in the insulating properties consisted mainly in a stabilization of the electrical properties close to the best values reported for SiO₂. The role of the oxygen is explained on the basis of annihilation of defects associated with oxygen vacancies in the SiO₄ tetrahedral chains.     

Effects of copper doping on the electronic properties of CdS films sintered with CdCl2

Chlorine- and copper-doped polycrystalline CdS films were prepared by coating a slurry which consisted of CdS, CdCl₂, CuCl₂ and propylene glycol on a glass substrate and sintering in a nitrogen atmosphere, to investigate the effects of copper doping on the window properties of all-polycrystalline CdS/CdTe heterojunction solar cells. The variations of carrier concentration as a function of the amount of copper doping in CdS films which were doped with the order of 10¹⁸ cm^–3 chlorine have been explained in terms of electronic compensation of the copper impurity. The variations of optical transmission spectra as a function of copper doping have been correlated with the variations of photoconductivity spectra. Even 10 p.p.m. copper in the sintered CdS films degrades the window properties of the CdS films significantly. The degradation is caused by reduced optical transmission rather than by an increase in electrical resistivity.     

Application of the electroreflectance technique to a three-medium system

The electroreflectance technique was applied to the case in which a thin dielectric film is present at a metal-electrolyte interface. The Ti/TiO₂H₂SO₄ system, in which an optical response characteristic of the TiO₂ film properties could be obtained for films with thicknesses of about five monolayers, was investigated experimentally. Photocurrent spectra were also obtained and information relevant to the properties of the very thin films was determined by a combination of these two optical techniques.     

The effect of post-annealing under CdCl<Subscript>2</Subscript> atmosphere on the properties of ITO thin films deposited by DC magnetron sputtering

Indium tin oxide (ITO) films deposited by DC magnetron sputtering were annealed under CdCl₂ atmosphere at different temperatures. The effects of CdCl₂ heat-treatment on the structural, electrical and optical properties of the films were investigated. The X-ray diffraction measurement proves the annealing results in a change of preferred orientation from (400) to (222). It is found the resistivity increases from 1.49 × 10⁻⁴ Ω cm of the as-deposited film to 6.82 × 10⁻⁴ Ω cm of the film annealed at 420 °C. The optical energy gap for the film varies from 3.97 to 3.89 eV. It is also found that the CdCl₂ heat-treatment results in narrowing the energy gap of ITO film.     

ITO thin films prepared by a microwave heating

ITO thin films were prepared by irradiating 2.45 GHz of microwave with an output power of 700 W using a commercial kitchen microwave oven. A substrate temperature went up and down rapidly between 100 and 650 °C in a minute by a dielectric loss of SnO₂ layer pre-deposited on a glass substrate. We found that the electrical and optical properties of films were affected by the atmosphere in a microwave irradiation, while the sintering was completed within a few minutes. Although the electrical resistivity was not reduced below 5.0 × 10^− 4 Ω·cm in this study, the results lead to the possibility of a practical rapid synthesis of ITO transparent conducting oxide films.     

Effects of heat treatment on properties of ITO films prepared by rf magnetron sputtering

Indium tin oxide (ITO) films were deposited on glass substrates by rf magnetron sputtering using a ceramic target (In₂O₃-SnO₂, 90-10 wt%) without extra heating. The post annealing was done in air and in vacuum, respectively. The effects of annealing on the structure, surface morphology, optical and electrical properties of the ITO films were studied. The results show that the increase of the annealing temperature improves the crystallinity of the films, increases the surface roughness, and improves the optical and electrical properties. The transmittance of the films in visible region is increased over 90% after the annealing process in air or in vacuum. The resistivity of the films deposited is about 8.125×10⁻⁴ Ω cm and falls down to 2.34×10⁻⁴ Ω cm as the annealing temperature is increased to 500°C in vacuum. Compared with the results of the ITO films annealed in air, the properties of the films annealed in vacuum is better.     

Positive flat band voltages measured on MIS diodes consisting of evaporated CdS films

SiO₂ films with very low losses have been produced by the decomposition of Si(C₂H₅O)₄ in an r.f. glow discharge. Loss-tangents of less than 10^-4 and break-down voltages of about 1 × 10⁷ V are obtainable by this method. The optical and electrical properties of these films are discussed.