Effect of annealing temperature on the decomposition of reactively sputtered Ag2Cu2O3 films

Ag₂Cu₂O₃ films were deposited on glass substrates by reactive sputtering of a composite silver-copper target. The deposited films were annealed in air at 100, 200 and 300 °C. The structure of the films was studied using X-ray diffraction (XRD), their surface morphology was characterised using scanning electron microscopy (SEM) and their electrical resistivity at room temperature was measured using the four point probe method. The 100 °C annealing did not modify either the film structure or the film morphology. On the other hand, Ag₂Cu₂O₃ films were partially decomposed into Ag and CuO after a 200 °C annealing. The decomposition was complete for a 300 °C annealing. The evolution of the film surface morphology as a function of the annealing temperature was discussed in connection to the evolution of the molar volume of the phases constituting the films.     

AlNxOy thin films deposited by DC reactive magnetron sputtering

AlN_xO_y thin films were produced by DC reactive magnetron sputtering, using an atmosphere of argon and a reactive gas mixture of nitrogen and oxygen, for a wide range of partial pressures of reactive gas. During the deposition, the discharge current was kept constant and the discharge parameters were monitored. The deposition rate, chemical composition, morphology, structure and electrical resistivity of the coatings are strongly correlated with discharge parameters. Varying the reactive gas mixture partial pressure, the film properties change gradually from metallic-like films, for low reactive gas partial pressures, to stoichiometric amorphous Al₂O₃ insulator films, at high pressures. For intermediate reactive gas pressures, sub-stoichiometric AlN_xO_y films were obtained, with the electrical resistivity of the films increasing with the non-metallic/metallic ratio.     

Effect of Al content on the properties of Cr1−xAlxC films prepared by RF reactive magnetron sputtering

Cr_1−xAl_xC films were deposited on high-speed steel by RF reactive magnetron sputtering. In this study, we aimed to identify the effect of the Al content on the properties of Cr_1−xAl_xC films. We found that Cr_1−xAl_xC films exhibited a fine columnar grain microstructure with some special characteristics, such as high hardness of Hv 1426, a low friction coefficient of 0.29, and a large contact angle of 90° for x = 0.18. Furthermore, an increase in Al content resulted in a decrease in film hardness and an increase in contact angle. Moreover, on annealing at 923 K, the mechanical properties of the films improved and a dense protective film of complex Cr₂O₃ and Al₂O₃ oxides was formed on the surface for better wear resistance, which will ultimately increase the lifetime of the high-speed steel substrate.     

Preparation and characterization of CrNxOy thin films: The effect of composition and structural features on the electrical behavior

Metallic oxynitrides have attracted the attention of several researchers in the last decade due to their versatile properties. Through the addition of a small amount of oxygen into a transition metal nitride film, the material's bonding states between ionic and covalent types can be tailored, thus opening a wide range of electrical, optical, mechanical and tribological responses. Among the oxynitrides, chromium oxynitride (CrN_xO_y) has many interesting applications in different technological fields. In the present work the electrical behavior of CrN_xO_y thin films, deposited by DC reactive magnetron sputtering, were investigated and correlated with their compositional and structural properties. The reactive gas flow, gas pressure, and target potential were monitored during the deposition in order to control the chemical composition, which depend strongly on reactive sputtering process. Depending on the particular deposition parameters that were selected, it was possible to identify three types of films with different growth conditions and physical properties. The electrical resistivity of the films, measured at room temperature, was found to depend strongly on the chemical composition of the samples.     

Structural and transport properties of cubic spinel ZnCo2O4 thin films grown by reactive magnetron sputtering

We report on the growth of cubic spinel ZnCo₂O₄ thin films by reactive magnetron sputtering and bipolarity of their conduction type by tuning of oxygen partial pressure ratio in the sputtering gas mixture. Crystal structure of zinc cobalt oxide films sputtered in an oxygen partial pressure ratio of 90% was found to change from wurtzite Zn_1−xCo_xO to spinel ZnCo₂O₄ with an increase of the sputtering power ratio between the Co and Zn metal targets, D_Co/D_Zn, from 0.1 to 2.2. For a fixed D_Co/D_Zn of 2.0 yielding single-phase spinel ZnCo₂O₄ films, the conduction type was found to be dependent on the oxygen partial pressure ratio: n-type and p-type for the oxygen partial pressure ratio below ∼70% and above ∼85%, respectively. The electron and hole concentrations for the ZnCo₂O₄ films at 300 K were as high as 1.37×10²⁰ and 2.81×10²⁰ cm⁻³, respectively, with a mobility of more than 0.2 cm²/V s and a conductivity of more than 1.8 S cm⁻¹.     

Gas barrier properties of titanium oxynitride films deposited on polyethylene terephthalate substrates by reactive magnetron sputtering

Titanium oxynitride (TiN_xO_y) films were deposited on polyethylene terephthalate (PET) substrates by means of a reactive radio frequency (RF) magnetron sputtering system in which the power density and substrate bias were the varied parameters. Experimental results show that the deposited TiN_xO_y films exhibited an amorphous or a columnar structure with fine crystalline dependent on power density. The deposition rate increases significantly in conjunction as the power density increases from 2 W/cm² to 7 W/cm². The maximum deposition rate occurs, as the substrate bias is −40 V at a certain power densities chosen in this study. The film's roughness slightly decreases with increasing substrate bias. The TiN_xO_y films deposited at power densities above 4 W/cm² show a steady Ti:N:O ratio of about 1:1:0.8. The water vapor and oxygen transmission rates of the TiN_xO_y films reach values as low as 0.98 g/m²-day-atm and 0.60 cm³/m²-day-atm which are about 6 and 47 times lower than those of the uncoated PET substrate, respectively. These transmission rates are comparable to those of DLC, carbon-based and Al₂O₃ barrier films. Therefore, TiN_xO_y films are potential candidates to be used as a gas permeation barrier for PET substrate.     

Structural and optical properties of Ga2(1−x)In2xO3 films prepared on α-Al2O3 (0 0 0 1) by MOCVD

Ga_2(1−x)In_2xO₃ thin films with different indium content x [In/(Ga + In) atomic ratio] were prepared on α-Al₂O₃ (0 0 0 1) substrates by the metal organic chemical vapor deposition (MOCVD). The structural and optical properties of the Ga_2(1−x)In_2xO₃ films were investigated in detail. Microstructure analysis revealed that the film deposited with composition x = 0.2 was polycrystalline structure and the sample prepared with x up to 0.8 exhibited single crystalline structure of In₂O₃. The optical band gap of the films varied with increasing Ga content from 3.72 to 4.58 eV. The average transmittance for the films in the visible range was over 90%.     

Properties of reactively sputtered Mo1−x O x films

Molybdenum oxide (Mo_1–xO_x) films were prepared by reactive rf sputtering of a Mo target in O₂/Ar plasma. The dependence of film properties on various sputtering parameters is investigated. The atomic percentage of oxygen (x) in the Mo_1–xO_x films decreases with sputtering power and increases with the partial pressure of oxygen. Mo_1–xO_x films that exhibit metallic conductivities can be obtained over a wide range of sputtering conditions. The intrinsic film stress of conducting Mo_1–xO_x is compressive. Such M_1–xO_x films were shown by backscattering spectrometry to be excellent diffusion barriers between Al and Si up to 600 °C annealing for 30 min.     

Chemical vapor deposition of ZrxTi1−xO2 and HfxTi1−xO2 thin films using the composite anhydrous nitrate precursors

Zr-Ti and Hf-Ti composite nitrates were successfully developed as single-source precursors for the chemical vapor deposition (CVD) of Zr_xTi_1−xO₂ and Hf_xTi_1−xO₂ thin films. The Zr-Ti nitrate can be assumed as a solid solution of the individual Zr and Ti nitrates, and the Zr/Ti molar ratio in the deposited Zr_xTi_1−xO₂ films is consistent with that in the precursor. The Hf-Ti nitrate appears to be a mixture of the Hf and Ti nitrates and the composition of the deposited Hf_xTi_1−xO₂ films depends remarkably on the heating time of precursor. Both Zr_xTi_1−xO₂ and Hf_xTi_1−xO₂ films exhibit trade-off properties between band gap and dielectric constant. The obtained results suggest that Zr_xTi_1−xO₂ and Hf_xTi_1−xO₂ films are promising candidates for gate dielectric application to improve the scalability and reduce the leakage current of the future complementary metal-oxide-semiconductor (CMOS) devices.     

Structural,thermal and electrical properties of the semiconductor system Ag(1−x)CuxInSe2

This paper presents a study of bulk samples synthesized of the Ag_1−xCu_xInSe₂ semiconductor system. Structural, thermal and electrical properties, as a function of the nominal composition (Cu content) x=0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 were studied. The influence of x on parameters such as melting temperature, solid phase transition temperature, lattice parameters, bond lengths, crystallite size t (coherent domain), electrical resistivity, electrical mobility and majority carrier concentration was analyzed. The electrical parameters are analyzed at room temperature. In general, it is observed that the properties of the Ag_1−xCu_xInSe₂ system for x≤0.4 are dominated by n-AgInSe₂, while for x>0.4, these are in the domain of p-CuInSe₂. The crystallite size t in the whole composition range (x) is of the order of the nanoparticles. Secondary phases (CuSe, Ag₂Se and InSe) in small proportion were identified by XRD and DTA.     

Superhydrophilic stability enhancement of RF co-sputtered TixSi1−xO2 thin films in dark

Ti_xSi_1−xO₂ compound thin-film systems were deposited by reactive RF magnetron co-sputtering technique. The effect of Ti concentration on the hydrophilicity of Ti_xSi_1−xO₂ compound thin films was studied and it was shown that the films with Ti_0.6Si_0.4O₂ composition possess the best hydrophilic property among all the grown samples. Surface ratio and average roughness of the thin films were measured by atomic force microscopy (AFM). Surface chemical states and stoichiometry of the films were determined by X-ray photoelectron spectroscopy (XPS). In addition, XPS revealed that the amount of Ti-O-Si bonds in nanometer depth from the surface of the Ti_0.6Si_0.4O₂ films was the maximum, which resulted in the most stable superhydrophilic property. According to XRD data analysis for the pure TiO₂ films, the polycrystalline anatase phase was formed with an average grain size of about 15 nm. Moreover, amorphous phase was also formed for the Ti_xSi_1−xO₂ compound systems due to presence of silicon in the films. Finally, optical properties of the films such as transmission, reflection and band gap energy were investigated using UV-vis spectrophotometry. It was found that the transmittance of the films was decreased with increasing Ti concentration in the films.     

Electrical and optical properties of silver doped indium oxide thin films prepared by reactive DC magnetron sputtering

Silver doped indium oxide (In_2−x Ag_x O_3−y) thin films have been prepared on glass and silicon substrates at room temperature (300 K) by reactive DC magnetron sputtering technique using an alloy target of pure indium and silver (80: 20 atomic %. The magnetron power (and hence the metal atom sputter flux) is varied in the range 40-80 W. The energy dispersive analysis of X-ray (EDAX) results show that the silver content in the film decreases with increasing magnetron power. The grain size of these films is of the order of 100 nm. The resistivity of these films is in the range 10⁻²-10⁻³ Ω cm. The work function of the silver-indium oxide films (by Kelvin Probe) are in the range: 4.64-4.55 eV. The refractive index of these films (at 632.8 nm) varies in the range: 1.141-1.195. The optical band gap of indium oxide (3.75 eV) shrinks with silver doping. Calculations of the partial ionic charge (by Sanderson's theory) show that silver doping in indium oxide thin films enhance the ionicity.     

Synthesis of nanocrystalline material by sputtering and laser ablation at low temperatures

Physical vapor deposition techniques such as sputtering and laser ablation – which are very commonly used in thin film technology – appear to hold much promise for the synthesis of nanocrystalline thin films as well as loosely aggregated nanoparticles. We present a systematic study of the process parameters that facilitate the growth of nanocrystalline metals and oxides. The systems studied include TiO₂, ZnO, γ-Al₂O₃, Cu₂O, Ag and Cu. The mean particle size and crystallographic orientation are influenced mainly by the sputtering power, the substrate temperature and the nature, pressure and flow rate of the sputtering gas. In general, nanocrystalline thin films were formed at or close to 300 K, while loosely adhering nanoparticles were deposited at lower temperatures. Received: 31 October 2000 / Accepted: 9 January 2001 / Published online: 26 April 2001     

Preparation and characterization of ZnSn-substituted barium ferrite thin films

The preparation of ZnSn-substituted barium ferrite films by sputtering deposition was studied. The as-sputtered films were amorphous, and annealing at a minimum of 750 °C was required to crystallize the films, based on the X-ray diffraction analysis and the magnetic measurements. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopic microanalysis confirmed that the films were single phase with the composition BaZn_xSn_xFe_12−2xO₁₉, x=0.2−0.3, and their thicknesses were 0.4-1.0 μm when annealed at 750-900 °C. Atomic and magnetic force microscopy studies showed no significant grain growth upon annealing and that the films consisted of single-domain grains forming interaction-cluster-type domains. The natural ferromagnetic resonance frequency was determined at around 4 GHz, together with substantial magnetic losses that make these films promising candidates for microwave absorbers.     

Evolution of the structural and optical properties of silver oxide films with different stoichiometries deposited by direct-current magnetron reactive sputtering

Nitrogen doping of silver oxide(AgxO) film is necessary for its application in transparent conductive film and diodes because intrinsic AgxO film is a p-type semiconductor with poor conductivity.In this work,a series of AgxO films is deposited on glass substrates by direct-current magnetron reactive sputtering at different flow ratios(FRs) of nitrogen to O2.Evolutions of the structure,the reflectivity,and the transmissivity of the film are studied by X-ray diffractometry and sphectrophotometry,respectively.The specular transmissivity and the specular reflectivity of the film decreasing with FR increasing can be attributed to the evolution of the phase structure of the film.The nitrogen does not play the role of an acceptor dopant in the film deposition.     

Effects of the sputtering power on the crystalline structure and optical properties of the silver oxide films deposited using direct-current reactive magnetron sputtering

This paper reports that a series of silver oxide (Ag_xO) films are deposited on glass substrates by direct-current reactive magnetron sputtering at a substrate temperature of 250 oC and an oxygen flux ratio of 15:18 by modifying the sputtering power (SP). The Ag_xO films deposited apparently show a structural evolution from cubic biphased (AgO + Ag₂O) to cubic single-phased (Ag₂O), and to biphased (Ag₂O + AgO) structure. Notably, the cubic single-phased Ag₂O film is deposited at the SP = 105 W and an AgO phase with <220> orientation discerned in the Ag_xO films deposited using the SP > 105 W. The transmissivity and reflectivity of the Ag_xO films in transparent region decrease with the increase the SP, whereas the absorptivity inversely increases with the increase of the SP. These results may be due to the structural evolution and the increasing film thickness. A redshift of the films' absorption edges determined in terms of Tauc formula clearly occurs from 3.1 eV to 2.73 eV with the increase of the SP.     

Growth and characterization of CuxS (x=1.0, 1.76, and 2.0) thin films grown by solution growth technique (SGT)

Thin films of Cu_xS (x=1.0, 1.76, and 2.0) were grown by solution growth technique (SGT). The deposition parameters such as pH of solution, deposition time, and deposition temperature were optimized. The deposited films were annealed in Ar atmosphere at 250 °C. The changes in structural and optical transport phenomenon of annealed films have been studied. The surface morphology and composition of films were studied by SEM micrographs and EDAX analysis, respectively, and the surface roughness was calculated by atomic force microscopy (AFM). The XRD study showed the polycrystalline nature of annealed film. The lattice parameters of different phases of the material were calculated from the XRD pattern. The absorption coefficient varies in the range of 1×10⁵-6×10⁵ cm⁻¹. The optical bandgaps of CuS, Cu_1.76S, and Cu₂S are 1.72, 2.11, and 2.48 eV, respectively.     

Influence of charged particle bombardment and sputtering parameters on the properties of HfO2 films prepared by dc reactive magnetron sputtering

HfO₂ films prepared on glass substrates by dc reactive magnetron sputtering in an Ar + O₂ atmosphere are investigated. The films are polycrystallized with a pure monoclinic phase, and the crystallization strongly relates to the technology environment. Charged particle bombardment mainly caused by negative oxygen ions during sputtering on the films results in rougher surface morphology and worse crystalline property. Influence of sputtering pressure, substrate temperature and Ar:O₂ flow ratio is studied. The main orientations of the films are (−1 1 1) and (1 1 1). The (−1 1 1) orientation is stable, but (1 1 1) orientation is very sensitive to the sputtering condition, and it can be suppressed effectively by introducing charged particle bombardment, lowing sputtering pressure and increasing oxygen concentration.     

Effect of substrate bias voltages on the diffusion barrier properties of Zr-N films in Cu metallization

Zr-N diffusion barriers were deposited on the Si substrates by rf reactive magnetron sputtering under various substrate bias voltages. Cu films were subsequently sputtered onto the Zr-N films by dc pulse magnetron sputtering without breaking vacuum. The Cu/Zr-N/Si specimens were then annealed up to 650 °C in N₂ ambient for an hour. The effects of deposition bias on growth rate, film resistivity, microstructure, and diffusion barrier properties of Zr-N films were investigated. An increase in negative substrate bias resulted in a decrease in deposition rate together with a decrease in resistivity. It was found that the sheet resistances of Cu/Zr-N(−200 V)/Si contact system were lower than those of Cu/Zr-N(−50 V)/Si specimens after annealing at 650 °C. Cu/Zr-N(−200 V)/Si contact systems showed better thermal stability so that the Cu₃Si phase could not be detected.