Structural and electrical resistivity characteristics of vacuum arc ion deposited zirconium nitride thin films

Zirconium nitride (ZrN) thin films were grown on glass and aluminum substrates using a dual cathodic arc ion deposition technique. The effects of various negative bias voltages and flow ratios of N₂/Ar on the stoichiometric ratio of nitrogen to zirconium (N/Zr), deposition rate, structure, surface morphology and electrical resistivity of the ZrN layer were investigated. Rutherford backscattering spectroscopy measurements indicated a drop in the deposition rate and a slight increase in stoichiometric ratio (N/Zr) with the increase of bias voltage up to −400 V, although the latter still remained slightly less than unity (~0.92). Deposition rate of the film showed an increase with the argon addition. X-ray diffraction patterns depicted mostly polycrystalline nature of the films, with preferential orientation of (2 0 0) planes in the −100 V to −300 V bias voltage range. For 70–50% nitrogen and at a bias voltage of −400 V, the (1 1 1) orientation of ZrN film predominated. The films were smoother at a lower bias of −100 V, while the roughness increased slightly at a higher bias voltage possibly due to (increased) preferential re-sputtering of zirconium-rich clusters/islands. Changes in the resistivity of the films were correlated with stoichiometry, crystallographic orientation and crystalline quality.     

Effect of electron irradiation on morphological,compositional and electrical properties of nanocluster carbon thin films grown using room temperature based cathodic arc process for large area microelectronics

The influence of 8 MeV electron beam bombardment on room temperature grown nanocluster carbon using cathodic arc process has been studied here. Atomic force microscopy (AFM) study shows that surface roughness varies with varying electron doses. High doses of electrons could causes thermal induce graphitization and morphological changes in the films. Raman spectroscopy analysis reveals that G-peak vary from 1555 cm⁻¹ to 1570 cm⁻¹ and D-peak varying from 1361 cm⁻¹ to 1365 cm⁻¹ indicating the disorderness and presence of both graphitic and diamond-like phases. Room temperature conductivity changes by two to three orders in magnitude. The conductivity in the films could be due to conduction of charge carriers through neighboring islands of conductive chains. Defect states calculated using the differential technique varies from 8 × 10¹⁷cm⁻³ eV⁻¹ to 1.5 × 10¹⁹ cm⁻³ eV⁻¹. Irradiation of nanocluster carbon thin films could be helpful to tune the electrical properties and defect densities of the nanocluster carbon films for various large area, flexible electronic and nano electronic applications.     

Influence of the nitrogen fraction on AlN thin film deposited by cathodic arc ion

Thin films of aluminum nitride (AlN) have been grown, using the cathodic arc ion deposition technique. The effects of nitrogen fractions in the discharge on synthesized films growth rate, stoichiometric ratio (N/Al), crystal orientation and molecular mode of vibration have been investigated. AlN films have been studied by means of Rutherford backscattering (RBS) spectroscopy, X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscope (SEM) and the four probe method. In RBS results, it has been found that growth rate and stoichiometric ratio decrease while reducing the nitrogen content in the synthesized chamber. XRD patterns indicated that films prepared in 100–85% nitrogen condition exhibit mixed phase of wurtzite+FFC, with preferential orientation along (002) corresponding to the hexagonal phase. It also demonstrated that at lower nitrogen environment, the transformation from mixed phase of wurtzite+FCC to a single phase of FCC–AlN occurs. FTIR spectroscopic analysis was employed to determine the nature of chemical bonding and vibrational phonon modes. Its spectra depicted a dominant peak around 850 cm⁻¹ corresponding to the longitudinal optical (LO) mode of vibration. A shift in the LO mode peak toward lower wavenumbers was noticed with the decrease of nitrogen fraction, illustrating the decline of nitrogen concentration in the deposited AlN films. The 75% nitrogen fraction appeared critical for AlN film properties, such as shifting of mixed (wurtzite+FCC) phase to single FCC–Al(N), a sharp drop of stoichiometric ratio and deposition rate. Measurements of resistivity recorded by the four probe method depicted a sharp decline in the corresponding growth condition.     

Electrical resistivity of thin electroless Ag–W films for metallization

It is shown that optimization of the electroless deposition and the use of vacuum annealing yield dramatic decrease in the resistivity and its scatter in 100- and 50-nm silver–tungsten (Ag–W) films. Physical processes, which control the resistivity drop during low-temperature annealing and the residue resistivity in the annealed films are discussed.     

Residual strain and electrical resistivity dependence of molybdenum films on DC plasma magnetron sputtering conditions

Sputter deposited molybdenum (Mo) thin films are used as back contact layer for Cu(In_1−xGa_x)(Se_1−yS_y)₂ based thin film solar cells. Desirable properties of Mo films include chemical and mechanical inertness during the deposition process, high conductivity, appropriate thermal expansion coefficient with contact layers and a low contact resistance with the absorber layer. Mo films were deposited over soda-lime glass substrates using DC-plasma magnetron sputtering technique. A 2³ full factorial design was made to investigate the effect of applied power, chamber pressure, and substrate temperature on structural, morphological, and electrical properties of the films. All the films were of submicron thickness with growth rates in the range of 34–82 nm/min and either voided columnar or dense growth morphology. Atomic force microscope studies revealed very smooth surface topography with average surface roughness values of upto 17 nm. X-ray diffraction studies indicated, all the films to be monocrystalline with (001) orientation and crystallite size in the range of 4.6–21 nm. The films exhibited varying degrees of compressive or tensile residual stresses when produced at low or high chamber pressure. Low pressure synthesis resulted in film buckling and cracking due to poor interfacial strength as characterized by failure during the tape test. Measurement of electrical resistivity for all the films yielded a minimum _value of 42 μΩ cm for Mo films deposited at 200 W DC power.     

Effects of substrate temperature on electrical and structural properties of copper thin films

This paper addresses the effects of substrate temperature on electrical and structural properties of dc magnetron sputter-deposited copper (Cu) thin films on p-type silicon. Copper films of 80 and 500 nm were deposited from Cu target in argon ambient gas pressure of 3.6 mTorr at different substrate temperatures ranging from room temperature to 250 °C. The electrical and structural properties of the Cu films were investigated by four-point probe and atomic force microscopy. Results from our experiment show that the increase in substrate temperature generally promotes the grain growth of the Cu films of both thicknesses. The RMS roughness as well as the lateral feature size increase with the substrate temperature, which is associated with the increase in the grain size. On the other hand, the resistivity for 80 nm Cu film decreases to less than 5 μΩ-cm at the substrate temperature of 100 °C, and further increase in the substrate temperature has not significantly decreased the film resistivity. For the 500 nm Cu films, the increase in the grain size with the substrate temperature does not conform to the film resistivity for these Cu films, which show no significant change over the substrate temperature range. Possible mechanisms of substrate-temperature-dependent microstructure formation of these Cu films are discussed in this paper, which explain the interrelationship of grain growth and film resistivity with elevated substrate temperature.     

Effect of Ar ion irradiation on structural and optical properties of e-beam evaporated cadmium telluride thin films

CdTe thin films were prepared using e-beam evaporation technique. The prepared films were irradiated by Ar⁺ ions at different fluencies using multipurpose aluminum (Al) probe as in-situ. This could also be used in ion bombardment for cleaning the substrate prior to coating. The as grown and Ar⁺ ion irradiated films were confirmed to be of polycrystalline nature with X-ray technique. Ar⁺ ion irradiation enhances the growth of (1 1 1) oriented CdTe crystals and the Cd enrichment on the surface of CdTe thin films. Higher Ar⁺ ion flux helps to grow (2 2 0) oriented CdTe thin film. A considerable change in structural parameters like crystallite size, lattice parameter, internal strain, etc. could be observed as a result of high Ar⁺ ion flux. The applied in-plan stress in both as grown and irradiated film was identified to be of tensile nature. The applied stress was observed between 0.016 and 0.067 GPa for all Ar⁺ ion irradiated samples. As a result of the Ar⁺ ion irradiation, the in-plan stress varies between 1.38×10⁹ and 5.58×10⁹ dyn/cm². The observed bad gap was increased for higher Ar⁺ ion flux. It shows the effect of Ar⁺ ion irradiation on the modifications of optical properties. The observed results were encouraging on the use of simple multipurpose Al probe for Ar⁺ ion irradiation process as in-situ.     

Effect of deposition rate and thickness on the structural and electrical properties of evaporated Ni/glass and Ni/Si(1 0 0) thin films

We have studied the effect of substrates [glass and Si(1 0 0)], of Ni thickness (t_Ni) and of the deposition rate [v₁=13 nm/min and v₂=22 nm/min] on the structural and electrical properties of evaporated Ni thin films. The Ni thickness, measured by the Rutherford backscattering (RBS) technique, ranges from 28 to 200 nm. From X-ray diffraction, it was found that all samples are polycrystalline and grow with the 〈1 1 1〉 texture. From the measure of the lattice constant, we inferred that Ni/Si samples are under a higher tensile stress than the Ni/glass ones. Moreover, in Ni/glass deposited at v₁, stress is relived as t_Ni increases while those deposited at v₂ are almost stress-free. The grain size (D) in Ni/glass with low deposition rate monotonously increases (from 54 to 140 Å) as t_Ni increases and are lower than those corresponding to Ni/Si. On the other hand, samples grown at v₂ have a constant D, for small t_Ni with D in Ni/glass larger than D in Ni/Si. Ni/glass deposited at low v₁ are characterized by a higher electrical resistivity (ρ) than those deposited at v₂. For the latter series, ρ is practically constant with t_Ni but decreases with increasing grain size, indicating that diffusion at the grain boundaries rather than surface effect is responsible for the variation of ρ in this thickness range. For the Ni/glass deposed at v₁ and the Ni/Si series, ρ has a more complex variation with thickness and deposition rate. These results will be discussed and correlated.     

不同离子比的锰钴镍薄膜材料结构和电学性能

采用磁控溅射法分别制备了不同组分的Mn-Co-Ni-O(MCNO)薄膜材料。通过对材料结构分析,发现在Mn离子数目不变的情况下,随着Co离子的增加,晶粒尺寸逐渐增大,且晶格常数先增大后减小;在Co离子数目不变的情况下,随着Mn离子的增加,薄膜的择优生长晶面由(311)不晶面向(400)晶面转变。对电学性能测试进行分析,可知薄膜材料既有Mn离子的导电机制,也有Co离子的导电机制;Mn_1.2Co_1.5Ni_0.3O₄具有最低的电阻率(235 Ω.cm),具有最高的室温负温度电阻系数︱a₂₉₅︱(4.7%.K_-1)值。     

Effect of annealing temperature on structural,electrical and optical properties of spray pyrolytic nanocrystalline CdO thin films

Nanocrystalline CdO thin films were prepared onto a glass substrate at substrate temperature of 300 °C by a spray pyrolysis technique. Grown films were annealed at 250, 350, 450 and 550 °C for 2.5 h and studied by the X-ray diffraction, Hall voltage measurement, UV-spectroscopy, and scanning electron microscope. The X-ray diffraction study confirms the cubic structure of as-deposited and annealed films. The grain size increases whereas the dislocation density decreases with increasing annealing temperature. The Hall measurement confirms that CdO is an n-type semiconductor. The carrier density and mobility increase with increasing annealing temperature up to 450 °C. The temperature dependent dc resistivity of as-deposited film shows metallic behavior from room temperature to 370 K after which it is semiconducting in nature. The metallic behavior completely washed out by annealing the samples at different temperatures. Optical transmittance and band gap energy of the films are found to decrease with increasing annealing temperature and the highest transmittance is found in near infrared region. The refractive index and optical conductivity of the CdO thin films enhanced by annealing. Scanning electron microscopy confirms formation of nano-structured CdO thin films with clear grain boundary.     

Preparation and electrical properties of inas thin films

Thin films of InAs have been deposited on mica substrates through a vacuum evaporation technique by means of controlling the substrate and source temperatures. The films with large crystal grain were found to have the best electrical properties. The maximum electron mobility of 12, 400 cm²/V·sec at room temperature was obtained in an undoped film of 3 Μm thickness at a donor concentration of 3.5 × 10¹⁶ cm⁻³. The temperature dependence of both electron mobility and resistivity of these films was slightly lower than those reported for bulk crystal type InAs.     

Impact of substrate temperature on the structural,optical and electrical properties of thermally evaporated SnS thin films

Tin Sulfide thin films were deposited on soda lime glass substrates at three different substrate temperatures using thermal evaporation technique. The impact of substrate temperature on the deposited films has been studied thoroughly. Surface morphology was modified with the substrate temperature. XRD spectra shows orthorhombic end-centered type SnS having (1 1 0) orientation. The crystallite size increases with the increase in the substrate temperature. At a high substrate temperature (450 °C) small grains form on the surface and crystallinity decreases. The effect of substrate temperature on optical and electrical properties has been studied using UV–Vis–NIR Spectrophotometer and Hall effect respectively. With the increase in the substrate temperature there is a substantial decrease in the transmittance and bandgap value. Refractive index (n), dielectric constant (ε₁) and extinction co-efficient (k) have also been calculated for different substrate temperatures.     

Effects of Sb,Zn doping on structural,electrical and optical properties of SnO2 thin films

Highly transparent, low resistive pure and Sb, Zn doped nanostructured SnO₂ thin films have been successfully prepared on glass substrates at 400° C by spray pyrolysis method. Structural, electrical and optical properties of pure and Sb, Zn doped SnO₂ thin films are studied in detail. Powder X-ray diffraction confirms the phase purity, increase in crystallinity, size of the grains (90–45 nm), polycrystalline nature and tetragonal rutile structure of thin films. The scanning electron microscopy reveals the continuous change in surface morphology of thin films and size of the grains decrease due to Sb, Zn doping in to SnO₂. The optical transmission spectra of SnO₂ films as a function of wavelength confirm that the optical transmission increases with Sb, Zn doping remarkably. The optical band gap of undoped film is found to be 4.27 eV and decreases with Sb, Zn doping to 4.19 eV, 4.07 eV respectively. The results of electrical measurements indicate that the sheet resistance of the deposited films improves with Sb, Zn doping. The Hall measurements confirm that the films are degenerate n-type semiconductors.     

Effect of the deposition rate on the phase transition in silver telluride thin films

Silver telluride thin films of thickness 50 nm have been deposited at different deposition rates on glass substrates at room temperature and at a pressure of 2×10⁻⁵ mbar. The electrical resistivity was measured in the temperature range 300–430 K. The temperature dependence of the electrical resistance of Ag₂Te thin films shows structural phase transition and coexistence of low temperature monoclinic phase and high temperature cubic phase. The effect of deposition rate on the phase transition and the electrical resistivity of silver telluride thin films in relation to carrier concentration and mobility are discussed.     

Effect of processing parameter on structural,optical and electrical properties of photovoltaic chalcogenide nanostructured RF magnetron sputtered thin absorbing films

The aim of this work was to develop high quality of CuIn_1−xGa_xSe₂ thin absorbing films with x (Ga/In+Ga)<0.3 by sputtering without selenization process. CuIn_0.8Ga_0.2Se₂ (CIGS) thin absorbing films were deposited on soda lime glass substrate by RF magnetron sputtering using single quaternary chalcogenide (CIGS) target. The effect of substrate temperature, sputtering power & working pressure on structural, morphological, optical and electrical properties of deposited films were studied. CIGS thin films were characterised by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Energy dispersive X-ray spectroscopy (EDAX), Atomic force microscopy (AFM), UV–vis–NIR spectroscopy and four probe methods. It was observed that microstructure, surface morphology, elemental composition, transmittance as well as conductivity of thin films were strongly dependent on deposition parameters. The optimum parameters for CIGS thin films were obtained at a power 100 W, pressure 5 mT and substrate temperature 500 °C. XRD revealed that thin film deposited at above said parameters was polycrystalline in nature with larger crystallite size (32 nm) and low dislocation density (0.97×10¹⁵ lines m⁻²). The deposited film also showed preferred orientation along (112) plane. The morphology of the film depicted by FE-SEM was compact and uniform without any micro cracks and pits. The deposited film exhibited good stoichiometry (Ga/In+Ga=0.19 and In/In+Ga=0.8) with desired Cu/In+Ga ratio (0.92), which is essential for high efficiency solar cells. Transmittance of deposited film was found to be very low (1.09%). The absorption coefficient of film was ~10⁵ cm⁻¹ for high energy photon. The band gap of CIGS thin film evaluated from transmission data was found to be 1.13 eV which is optimum for solar cell application. The electrical conductivity (7.87 Ω⁻¹ cm⁻¹) of deposited CIGS thin film at optimum parameters was also high enough for practical purpose.     

Electrical and structural characteristics of tin-doped GaN thin films and its hetero-junction diode made all by RF reactive sputtering

Tin (Sn) doping in gallium nitride (GaN) has been mainly reported from the theoretical view only. Based upon the availability of Sn precursor and commercialization, Sn-GaN film has not been deposited magnetron sputtering until this work. By using the cheap and safe reactive sputtering technique, here we present Sn-GaN thin films with single cermet targets at the Sn/(Sn+Ga) molar ratios of x=0, 0.03, 0.07, and 0.1 to form Sn-x-GaN films under the atmosphere of the mixture of Ar and N₂. The Sn-GaN films had the wurtzite structure. Sn can be added to GaN to form SnGaN alloy with a maximal amount of ~10%. The structural, electrical, and optical properties had changed with the Sn content until the oversaturation of Sn in Sn-0.1-GaN. The Sn doping led to the lattice expansion, worsened crystallinity, n-type GaN, increased electrical concentration, decreased the electrical mobility etc. Moreover, n-Sn-x-GaN/p-Si diodes were successfully made and their performance was evaluated in terms of the barrier height, ideality factor, and series resistance. This work has opened the door for studying the different kinds of dopants on the important III nitrides.     

制备工艺对ITO薄膜的电阻率及沉积速率的影响

采用射频磁控溅射法制备了氧化铟锡[ITO,In2O3:SnO2=90:10(质量比)]薄膜,详细探讨了溅射气氛氧氩体积比、溅射功率及溅射气压对ITO薄膜电阻率和沉积速率的影响。结果表明:溅射工艺参数对ITO薄膜电阻率和沉积速率的影响十分明显。随着氧氩体积比的增大,样品的电阻率显著增大,沉积速率下降;随着溅射功率的增加,ITO薄膜的电阻率先减小后略微增大,沉积速率上升;随着溅射气压升高,ITO薄膜的电阻率先减小后增大,当溅射气压增大到较大值时,ITO薄膜的电阻率又开始减小,而沉积速率则先上升后下降。     

Influence of heat treatment on the structural,optical and electrical properties of Cd20Sn10Se70 thin films

The effect of annealing temperature (T_a) on the structural, optical, and electrical properties of thermally evaporated Cd₂₀Sn₁₀Se₇₀ thin films has been investigated. Differential Thermal Analysis (DTA) was used to determine the glass transition temperature (T_g) of the prepared alloy. X-ray diffraction studies showed that the as-deposited film and the films that were annealed at T_a<T_g are of low crystallinity. On annealing above T_g, these films showed a polycrystalline nature. The surface morphology and microstructure of as-deposited and annealed films have been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Their optical constants were calculated from the transmittance measurements in the range 200–2500 nm. The dispersion of refractive index was analyzed in terms of the single-oscillator Wemple-Di Domenico model. Analysis of the optical absorption data indicates that the optical band gap E_g of these films obeys Tauc׳s relation for the allowed direct transition. The optical band gap E_g as well as the activation energy for the electrical conduction ∆E were found to increase with increase of annealing temperature up to T_g, whereas above T_g there is a remarkable decrease in both E_g and ∆E. The obtained results were interpreted in terms of the Mott-Davis model and amorphous–crystalline transformation.     

Effect of 80 MeV Au ions irradiation on CuInTe2 single crystals grown by CVT technique

Single crystals of CuInTe₂ (CIT) have been grown by the chemical vapor transport (CVT) technique using iodine as the transporting agent. CIT crystals were irradiated with 80 MeV Au⁸⁺ ions at room temperature at different fluences. The surface roughness was measured using an atomic force microscope (AFM). It was found to increase from 9.319 nm in the as-grown sample to 61.169 nm in the sample irradiated with a fluence of 1×10¹³ ions/cm². The intensities of the X-ray diffraction peaks corresponding to the (112) and (004/200) planes of the irradiated sample decrease with respect to the fluences. The full-width at half-maximum (FWHM) of X-ray rocking curves was measured as a function of different ion fluences. The FWHW increases with increase of ions fluences. This is attributed to the irradiation-induced partial amorphization of the top surface of the CIT crystals. The fall in absorption coefficients with photon energy is sharper for as-grown samples than irradiated samples. The band gap value gradually decreases from 1.04 to 0.977 eV upon Au⁸⁺ ions’ irradiation with a fluence of 1×10¹³ ions/cm². Photoluminescence (PL) measurements show a red shift compared to the as-grown CIT single crystals. The Raman modes of A₁ (high) and E and/or B₂ (LO) are observed at 123 and 173 cm⁻¹ in as-grown CIT single crystals, respectively. As the ion fluence is increased, the Raman frequency increases and the curves broaden. The above observed features are related to the large electronic energy transfer of the Au beam to the CIT crystals.     

Effect of fluorine doping on the structural,optical and electrical properties of spray deposited cadmium stannate thin films

Cadmium stannate (Cd₂SnO₄) thin films were coated on Corning 1737 glass substrates at 540 °C by spray pyrolysis technique, from the aqueous solution of cadmium acetate and tin (II) chloride precursors. Fluorine doped Cd₂SnO₄ (F: Cd₂SnO₄) thin films were prepared by adding ammonium fluoride in the range of 0–5 wt% of the total weight of cadmium acetate and tin (II) chloride in the spray solution. Thickness of the prepared films is about 300 nm. X-ray diffraction analysis of the Cd₂SnO₄ and 3 wt% F: Cd₂SnO₄ films shows the signature for the growth along (222) direction. Scanning electron micrographs showed that fluorine doping effectively modifies the surface morphology of Cd₂SnO₄ films. Average optical transmittance in the visible region (500–850 nm) for Cd₂SnO₄ is ~79% and it is increased to ~83% for 1 wt% doping concentration of the NH₄F in the solution. Fluorescence spectra of F: Cd₂SnO₄ (1 wt% and 3 wt%) exhibit peak at 601 nm. F: Cd₂SnO₄ film (1 wt%) shows mobility of ~42 cm²/V s, carrier concentration of ~9.5×10¹⁹ cm^?3 and resistivity of ~1.5×10^?3 Ω cm.