Structural and electrical properties of RuO2 thin films prepared by rf-magnetron sputtering and annealing at different temperatures

Conductive ruthenium oxide (RuO₂) thin films have been deposited at different substrate temperatures on various substrates by radio-frequency (rf) magnetron sputtering and were later annealed at different temperatures. The thickness of the films ranges from 50 to 700 nm. Films deposited at higher temperatures show larger grain size (about 140 nm) with (200) preferred orientation. Films deposited at lower substrate temperature have smaller grains (about 55 nm) with (110) preferred orientation. The electrical resistivity decreases slightly with increasing film thickness but is more influenced by the deposition and annealing temperature. Maximum resistivity is 861 μΩ cm, observed for films deposited at room temperature on glass substrates. Minimum resistivity is 40 μΩ cm observed for a thin film (50 nm) deposited at 540°C on a quartz substrate. Micro-Raman investigations indicate that strain-free well-crystallized thin films are deposited on oxidized Si substrates.     

Reactive pulsed laser deposition of thin molybdenum- and tungsten-nitride films

In this work reactive pulsed laser deposition of molybdenum- and tungsten-nitride thin films is investigated. Metallic targets were ablated in low-pressure (1, 10 and 100 Pa) nitrogen atmosphere by KrF excimer laser pulses (fluence ∼6.5 J/cm²). Films were deposited on silicon wafers heated to ∼25, 250 and 500 °C. The characteristics of the films strongly depend on the N₂ pressure. By increasing N₂ pressure, the nitrogen content increases in the films, which leads to a monotonous increase of the electrical resistivity. Deposition rate decreases at 100 Pa as indicated by Rutherford backscattering spectrometry. At this pressure, hardness of the films significantly decreases also, as shown by microhardness measurements. X-ray diffractometry shows that films crystallinity is improved by increasing the substrate temperature. In addition, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were applied for visualising the film surface.     

Properties of spray deposited niobium oxide thin films

Niobium Oxide (Nb₂O₅) thin films were deposited on the glass substrates, using spray pyrolysis technique. During deposition the preparative parameters like nozzle to substrate distance, spray rate, concentration of the sprayed solution were kept constant at optimized values. The effect of substrate (deposition) temperature (varied between 250 to 450°C) and post annealing treatment (at temperature 500°C) on the structural, optical and electrical properties of thin films were studied. Using scanning electron microscopy and X-ray diffraction technique morphological and structural characterizations of the films were carried out. For optical and electrical properties of thin films, optical absorption and two probe electrical resistivity techniques were used. It has been observed that with increase in the substrate temperature films become micro or polycrystalline. Annealed films exhibit higher crystallinity. Other parameters like thickness, electrical resistivity and band gap energy value decrease with increase in substrate temperature.     

Electrical properties of thin metal zinc films

Thin metal zinc films 40 to 200 nm thick are deposited by thermal evaporation at room temperature onto glass substrates with a deposition rate of 0.2 to 0.7 nm sec^–1. The electrical resistivity is measured as a function of film thickness, deposition rate and annealing temperature. The experimental results show that electrical resistivity decreases as the film thickness, deposition rate and annealing temperature increase, while the temperature coefficient of resistivity increases with the increase in the film thickness. The calculated values of the activation energy for the conduction electrons increases as the film thickness and deposition rate increase. The well known Fuchs-Sondheimer model is applied for zinc films. The theoretically calculated values for the electrical resistivity and the temperature coefficient of resistivity are in good agreement with the experimental results.     

Effects of temperature on the resistivity of vacuum deposited Cu-MgF2 cermet thin films: an investigation of conduction mechanism

Cermet thin films of Cu-MgF₂ were deposited onto glass substrates using a conventional resistive heating co-evaporation technique. Films of starting compositions 40, 60 and 80 vol % Cu and average thicknesses 60, 145 and 285 nm were deposited at elevated substrate temperatures between 300 and 393 K in a vacuum of 1.33 × 10^–3 Pa. Room temperature D.C. resistivity measurements were performed at atmospheric pressure from which activation energies and TCRs for the cermet films were determined. It was observed that the resistivity () data fitted into the ln 1/T relationship. The activation energies were found to decrease with increase in film thickness and increase in metallic content of the cermet films whilst the TCRs were all negative. From the trends in both activation energies and TCRs it was concluded that the predominant conduction mechanism was tunnelling of thermally activated charge carriers.     

Preparation and study of thickness dependent electrical characteristics of zinc sulfide thin films

Zinc sulfide thin films have been deposited onto glass substrates by chemical bath deposition. The various deposition parameters such as volume of sulfide ion source, pH of bath, deposition time, temperature etc are optimized. Thin films of ZnS with different thicknesses of 76–332 nm were prepared by changing the deposition time from 6–20 h at 30° C temperature. The effect of film thickness on structural and electrical properties was studied. The electrical resistivity was decreased from 1.83 × 10⁵ Ω-cm to 0.363 × 10⁵ Ω-cm as film thickness decreased from 332 nm to 76 nm. The structural and activation energy studies support this decrease in the resistivity due to improvement in crystallinity of the films which would increase the charge carrier mobility and decrease in defect levels with increase in the thickness.     

The influence of thickness and deposition temperature on the conduction activation energy of CdSe0.2Te0.8 thin films

The electrical conductivity and stability in resistance of CdSe_0.2Te_0.8 thin films in different ambients and deposited at different substrate temperatures were investigated. A reduction in conduction activation energy with increase in film thickness and deposition temperature is accounted for by the fact that in CdSe _x Te_1–x inhomogeneous semiconductor thin films, the potential relief inhomogeneity may be reduced with increase in film thickness and substrate temperature, which results in the decrease of conduction activation energy of the films.     

The growth of single crystal films of silver on rocksalt by sputtering

Thin films of silver on rocksalt have been prepared by diode sputtering in an argon discharge. Deposition rate, substrate temperature, and film thickness have been varied, and dependence of orientation on these parameters has been studied. Within a deposition rate range of 0.1 to 1.15Å/sec, films have been grown with (100) [110]_Ag / / (100) [110]_NaCl orientation, at temperatures in the range –35 to 0° C. Higher rates required higher temperatures. Films giving these results were all 200 Å in thickness. A thickness dependence of orientation has been observed for films below 120 Å in thickness.The above results are discussed in terms of the effect of arrival energy of the sputtered material at the substrate. The results of calculations, on the effect of gas pressure on the arrival energy, are presented and it is shown that, at 10^–2 torr, up to 15% of the arriving atoms will have energies above 0.6 eV. That the observed rate, temperature, and thickness dependence of epitaxy are due to surface cleaning and penetration effects caused by the energy of arrival of the atoms is shown to be possible.The effect of charged particle bombardment of the substrate is also considered. It is shown that this may also be an important parameter affecting the growth.     

Sputter deposition of semicrystalline tin dioxide films

Tin dioxide is emerging as an important material for use in copper indium gallium diselenide based solar cells. Amorphous tin dioxide may be used as a glass overlayer for covering the entire device and protecting it against water permeation. Tin dioxide is also a viable semiconductor candidate to replace the wide band gap zinc oxide window layer to improve the long-term device reliability. The film properties required by these two applications are different. Amorphous films have superior water permeation resistance while polycrystalline films generally have better charge carrier transport properties. Thus, it is important to understand how to tune the structure of tin dioxide films between amorphous and polycrystalline. Using X-ray diffraction (XRD) and Hall-effect measurements, we have studied the structure and electrical properties of tin dioxide films deposited by magnetron sputtering as a function of deposition temperature, sputtering power, feed gas composition and film thickness. Films deposited at room temperature are semicrystalline with nanometer size SnO₂ crystals embedded in an amorphous matrix. Film crystallinity increases with deposition temperature. When the films are crystalline, the X-ray diffraction intensity pattern is different than that of the powder diffraction pattern indicating that the films are textured with (101) and (211) directions oriented parallel to the surface normal. This texturing is observed on a variety of substrates including soda-lime glass (SLG), Mo-coated soda-lime glass and (100) silicon. Addition of oxygen to the sputtering gas, argon, increases the crystallinity and changes the orientation of the tin dioxide grains: (110) XRD intensity increases relative to the (101) and (211) diffraction peaks and this effect is observed both on Mo-coated SLG and (100) silicon wafers. Films with resistivities ranging between 8 mΩ cm and 800 mΩ cm could be deposited. The films are n-type with carrier concentrations in the 3 × 10¹⁸ cm^− 3 to 3 × 10²⁰ cm^− 3 range. Carrier concentration decreases when the oxygen concentration in the feed gas is above 5%. Electron mobilities range from 1 to 7 cm²/V s and increase with increasing film thickness, oxygen addition to the feed gas and film crystallinity. Electron mobilities in the 1-3 cm²/V s range can be obtained even in semicrystalline films. Initial deposition rates range from 4 nm/min at low sputtering power to 11 nm/min at higher powers. However, deposition rate decreases with deposition time by as much as 30%.     

The electrical properties of polycrystalline ZnIn2Te4 thin films

Thin films of ZnIn₂Te₄ are grown onto glass substrates by the flash evaporation technique. Electrical properties such as electrical resistivity and activation energy were studied with different substrate temperatures ranging from 300 to 623 K. It is observed that the film grown at a substrate temperature of 523 K is a single phase polycrystalline stoichiometric film with minimum electrical resistivity. The effect of the film thickness on the electrical properties of ZnIn₂Te₄ thin films grown at a substrate temperature of 523 K has been studied. The experimental data can be satisfactorily explained on the basis of the Fuchs-Sondheimer theory.     

Band gap and intergrain barrier activation energies in Bi90Sb10 thin films

The electrical resistivity and Hall effect measurements have been made on vacuum evaporated Bi₉₀ Sb₁₀ alloy films of various thickness (350 A to 4500 A), in the temperature range of 77 to 510 K. As observed earlier, the alloy system behaves like a semiconductor, but with a band gap quite higher than previously reported for bulk single crystals. Also a kind of intergrain barrier is found in these films. The activation energy of these barriers is found to decrease with increasing film thickness and substrate temperature. This trend agrees with the earlier observations in other materials and also in the same alloy system. The higher band gaps in these films are attributed to quantum size effect and high dislocation density in these films. The decrease in the inter-grain barrier activation energy with increasing thickness and substrate temperature has been attributed to increased grain size of the films.     

On the annealing temperature, penetration depth of oxygen and film thickness on the DC and AC electrical properties and nano-structure of Ti thin films

Ti films of different thickness ranging from 12.3 to 246.2 nm were deposited, using resistive heat method and post-annealed at different temperatures with a flow of 5 cm³ s⁻¹ oxygen. The nano-structures of the films were obtained using X-ray diffraction (XRD) and atomic force microscopy (AFM). The results showed an initial reduction of the grain size at 373 K annealing temperature and increase of the grain size at higher temperatures. The cause of this was due to the reaction of oxygen with Ti atoms which breaks up the Ti grains and hence needle-like features form. The enhancement of activation processes at higher temperatures results in larger grains. The analysis of XRD in conjunction with AFM images showed that those films containing (004) line of anatase phase and sub-oxide phases of titanium oxide also show two types of grains in the AFM images. The resistivity of the film increased with annealing temperature, which is due to competition between increased diffusion rate and the increased reaction rate of oxygen with Ti atoms. The Hall coefficient R_H and the mobility μ decreased with increasing film thickness at all annealing temperatures, while R_H increases and μ decreases with increasing the annealing temperature. The carrier concentration increased with film thickness and decreased with annealing temperature. The impedance spectroscopy showed that all films have a pure RC behaviour, where the magnitude of R depends on the annealing temperature and film thickness. The apparent activation energies E_a, obtained from three different methods, namely σ, R_H and grain size showed good agreement within 0.30-0.46 eV for the range of film thickness examined in this work. It was found that films with thickness less than 70 nm can be recognized as Ti-oxide films while thicker films are only surface-oxidised Ti films.     

Structural evolution,electrical and optical properties of AZO films deposited by sputtering ultra-high density target

Aluminum-doped zinc oxide (AZO) target was fabricated using AZO nanopowders synthesized by co-precipitation method and then the AZO films with different thicknesses were deposited on glass by d.c. magnetron sputtering at room temperature. AZO target is nodules free and shows homogeneous microstructure, ultra-high density and low resistivity. ZnAl₂O₄ phase appears in AZO target and disappears in AZO films. All AZO films show c-axis preferred orientation and hexagonal structure. With increasing film thickness from 153 to 1404 nm, the crystallinity was improved and the angle of (002) peak was close to 34.45°. The increase in grain size and surface roughness is due to the increase in film thickness. The decrease of resistivity is ascribed to the increases of carrier concentration and Hall mobility. The lowest resistivity is 9.6 × 10^?4 Ω·cm. The average transmittance of AZO films exceeds 80%, and a sharp fundamental absorption edge with red-shifting is observed in the visible range. The bandgap decreases from 3.26 to 3.02 eV.     

Effect of some growth parameters on vacuum-deposited CulnSe2 films

P-type copper indoselenide (CulnSe₂) thin films were vacuum-deposited on glass substrates by a single-source thermal evaporation technique under different conditions of preparation. The structural properties of the films were investigated by X-ray diffraction and transmission electron microscopy and diffraction techniques. The dark resistivity of the deposited films was investigated as a function of film thickness, deposition rate and substrate temperature. The conductivity activation energy ranges from 0.851 to 1.01 eV depending on the deposition rate. Single-phase and stoichiometric CulnSe₂ films could be deposited at low deposition rates (less than 4 nms^–1). Higher deposition rates led to multiphase films containing InSe, ln₂Se₃, CuSe and Cu₃Se₂ in addition to CulnSe₂.     

Physical properties of tin oxide films deposited by oxidation of SnCl2

Highly transparent and conducting SnO₂ films, as required in thin film heterojunction solar cells, were deposited onto Pyrex glass substrates by oxidation of SnCl₂ in the temperature range 350–500°C. Oxygen with a flow rate of between 1 and 3.251 min^-1 was used as both the carrier gas and the oxidizing agent. For films deposited in these conditions the resistivity varies from 10^-2 to 10^-3 Ω cm with transmission in the range 87%–71%. It was observed that both the resistivity and the transmission decrease with increasing deposition temperature. The resistivity of films deposited at a fixed deposition temperature passes through a minimum as the oxygen flow rate is increased. Hence, SnO₂ films with low resistivity and high transmission can be produced by the oxidation of SnCl₂ at relatively low temperatures using the oxygen flow rate corresponding to the minimum resistivity. For example, in the present work, low resistivity (4.4 × 10^-3 Ω cm) and high transmission (87%) were observed for films deposited at 400°C with an oxygen flow rate of 1.81 min^-1. The effects of the deposition temperature, oxygen flow rate and deposition time on the thickness, deposition rate, resistivity and absorption coefficient are discussed in detail.     

Synthesis and characterization of platinum thin film as top electrodes for multifunctional layer devices by PLD

Platinum thin films were grown onto (001) oriented SrTiO₃ substrates by means of the pulsed laser deposition technique. Structural and morphological characterizations were performed using XRD and AFM. The influence of substrate temperature and deposition rate was analyzed on the crystallographic properties of the film. As a result, an increment in the crystallinity of the film due to the change on the temperature was observed. On the other hand, Pt films showed a granular morphology and its roughness was related to the fluence and low deposition temperature. Finally their electrical properties were analyzed and discussed as a function of the previous morphological results.     

Electrical properties of vacuum evaporated PbSnS3 thin films

Electrical conduction of evaporated PbSnS₃ films of thickness ranging between 0.1 and 2.0 μm were studied by measuring the dc current in both parallel (planar) and transverse (cross plane) directions to the substrate surface. Conduction mechanisms relevant to various regions of the current-voltage characteristics are discussed. The obtained film conductivities were of the order 10⁻⁵ S cm⁻¹ at room temperature and increased exponentially with increasing temperature. No consistent modification of the conductivity values and nature were observed when the films are doped with CdCl₂, PbCl₂ and CuI impurities. While planar conductivity activation energies were constant with voltage and increased slightly with deposition temperature, the cross plane values were found to depend on both voltage and film deposition temperature.     

Substrate temperature dependent morphology and resistivity of pulsed laser deposited iridium oxide thin films

Iridium oxide (IrO₂) thin films were deposited on Si (100) substrates by means of pulsed laser deposition technique at various substrate (deposition) temperatures ranging from 250 to 500 °C. Effects of substrate temperature on the crystalline nature, morphology and electrical properties of the deposited films were analyzed by using X-ray diffraction, Raman spectroscopy, Scanning electron microscopy and four-point probe method. It was found that the above properties were strongly dependent on the substrate temperature. The as-deposited films at all substrate temperatures were polycrystalline tetragonal IrO₂ and the preferential growth orientation changed with the substrate temperature. IrO₂ films exhibited fairly homogeneous thickness and good adhesion with the substrate, the average feature size increases with the substrate temperature. The room-temperature resistivity of IrO₂ films decreased with the increase of substrate temperature and the minimum resistivity of (42 ± 6) μΩ cm was obtained at 500 °C. The resistivity of IrO₂ films correlated well with the corresponding film morphology changes.     

Indium-doped ZnO thin films deposited by the sol–gel technique

Conducting and transparent indium-doped ZnO thin films were deposited on sodocalcic glass substrates by the sol–gel technique. Zinc acetate and indium chloride were used as precursor materials. The electrical resistivity, structure, morphology and optical transmittance of the films were analyzed as a function of the film thickness and the post-deposition annealing treatments in vacuum, oxygen or argon. The obtained films exhibited a (002) preferential growth in all the cases. Surface morphology studies showed that an increase in the films' thickness causes an increase in the grain size. Films with 0.18 μm thickness, prepared under optimal deposition conditions followed by an annealing treatment in vacuum showed electrical resistivity of 1.3 × 10^− 2 Ωcm and optical transmittance higher than 85%. These results make ZnO:In thin films an attractive material for transparent electrodes in thin film solar cells.     

Effect of processing conditions on microstructure and electrical characteristics of Ni thin films

Ni thin films with an intermediate layer of Cr were prepared by using dc magnetron sputtering under different conditions. Effects of deposition temperature, post-deposition annealing on the microstructure and the electrical characteristics were investigated. The relationship between film microstructure and its resistivity was analyzed. It was found that the crystal grains aggregated into large ones when the deposition temperature reached or exceeded 150 °C. This could be explained that high deposition temperature conduced high activation energy, which increased surface mobility of the adatoms. Annealing treatments resulted in the densification of the films. Resistivity of the films strongly depended on grain size and crystallinity. The influence of Cr intermediate layer on the resistivity was also discussed. Compared to annealing treatment, the deposition temperature exhibited larger controlling effect on film resistivity.