Hydrogenated amorphous silicon nitride deposited by DC magnetron sputtering

Hydrogenated amorphous silicon nitride thin films are deposited by DC magnetron sputtering in argon, and molecular hydrogen and nitrogen mixture. The samples are characterized by electrical measurements and by optical transmission. The physicochemical structure is studied by FTIR spectrum analysis. The results show that both nitrogen and hydrogen are incorporated. The ratio [N]/[Si] increases with increasing hydrogen partial pressure. The deposited films are used in MIS structures. The capacitance–voltage characteristics are carried out. The deposited samples present a large gap and show a nearly chemical stoichiometric composition.     

Optical and physicochemical properties of hydrogenated silicon nitride thin films: Effect of the thermal annealing

The effect of thermal annealing on the optical and physicochemical properties of hydrogenated silicon nitride films was studied. These films were deposited by plasma-enhanced chemical vapor deposition from a mixture of silane, ammonia, and nitrogen. Subsequently, the films were annealed at various temperatures ranging from 400°C to 1000°C. The properties of the films were studied using ellipsometry and Fourier transform infrared spectroscopy. The Maxwell Garnet model considers the silicon nitride material as heterogeneous with three distinct phases: silicon, stoichiometric silicon nitride, and hydrogen. Based on the ellipsometric analysis, the annealing treatment leads to reduce the volume fraction of both hydrogen and silicon. As a result, the stoichiometry parameter significantly increases from 1.24 to 1.32 making it closer to the stoichiometric silicon nitride one. According to the infrared data, a noticeable decrease in the total hydrogen concentration in the films was obtained with respect to the annealing temperature.     

Investigations on non-stoichiometric zirconium nitrides

Non-stoichiometric zirconium nitride thin films were prepared by reactive dc magnetron sputtering. Structural, optical and electrical properties were investigated with respect to nitrogen gas flow. The film characterization was obtained through various techniques: Rutherford back scattering (RBS), X-ray diffraction (XRD), reflectometry and a four probe method. We found that the deposition rate decreases while the nitrogen flow increases. Also it was shown that a stoichiometric compound (ZrN) is formed at a 4 sccm nitrogen flow. It has a rock-salt structure and presents a minimum of resistivity and a gold-like color. As nitrogen flow increases, films become more and more amorphous, semi-transparent and electrically resistive. Furthermore, at a nitrogen flow of 9 sccm, the nitrogen to zirconium atomic concentration ratio is near 1.33 and the film exhibits properties close to those of a Zr₃N₄ phase.     

Optical and electrical properties of p-type transparent conducting CuAlO2 thin film synthesized by reactive radio frequency magnetron sputtering technique

Thin films of p-type transparent conducting CuAlO₂ have been synthesized through reactive radio frequency magnetron sputtering on silicon and glass substrates at substrate temperature 300°C. Reactive sputtering of a target fabricated from Cu and Al powder (1:1.5) was performed in Ar+O₂ atmosphere. The deposition parameters were optimized to obtain phase pure, good quality CuAlO₂ thin films. The films were characterized by studying their structural, morphological, optical and electrical properties.     

Synthesis and characterization of Al-N codoped p-type ZnO epitaxial films using high-temperature homo-buffer layer

Al-N codoped p-type ZnO thin films have been prepared by DC magnetron reactive sputtering reproducibly using a high-temperature (HT) homo-buffer layer. The influence of HT buffer layer deposition time (T_ht) on film properties was investigated by X-ray diffraction (XRD), scanning electron micro-spectra (SEM) and Hall measurement. The Al-N codoped ZnO film was improved evidently in its crystal quality by varying the value of T_ht. Results of Hall effect showed that all of the Al-N codoped ZnO thin films were p-type conduction and had resistivity mainly below 50 Ω cm. The optimum deposition time of HT buffer layer is around 3 min from the comprehensive consideration of structural, electrical, and optical properties. The obtained ZnO thin film can meet the need of application in optoelectronic devices based on ZnO.     

Structural and optical properties of zinc nitride films prepared by rf magnetron sputtering

Zinc nitride films were prepared on quartz substrates by rf magnetron sputtering using pure zinc target in N₂-Ar plasma. X-ray diffraction (XRD) analysis indicates that the films just after deposition are polycrystalline with a cubic structure and a preferred orientation of (4 0 0). X-ray photoelectron spectroscopy (XPS) analysis also confirms the formation of N-Zn bonds and the substitution incorporation of oxygen for nitrogen on the surface of the films. The optical band gap is calculated from the transmittance spectra of films just after deposition, and a direct band gap of 1.01 ± 0.02 eV is obtained. Room temperature PL measurement is also performed to investigate the effect of defect on the band gap and quality of the zinc nitride films.     

Influence of N2 flow ratio on the properties of hafnium nitride thin films prepared by DC magnetron sputtering

Hafnium nitride (Hf-N) thin films were deposited on fused silica at different N₂ flow ratio (N₂/N₂ + Ar) using a reactive DC magnetron sputtering system. A gradual evolution in the composition of the films from Hf₃N₂, HfN, to higher nitrides was found through X-ray diffraction (XRD). Films of Hf₃N₂ and HfN show positive temperature coefficients of resistivity, while higher nitride has a negative one. Highly oriented growth of (0 0 1) Hf₃N₂ and NaCl-structure (1 0 0) HfN films were fabricated on fused silica substrate at relatively lower temperature of 300 °C. The electrical resistivity values of both as-deposited and post-deposition annealed films were measured by a four-point probe method. The obtained minimum resistivity of as-deposited film is 20 μΩ cm, and this result shows potential application of HfN films as electrode materials in electronic devices.     

VO2 thin films based active and passive thermochromic devices for energy management applications

VO₂ thin films were fabricated by argon ion beam assisted non-reactive ac dual magnetron sputtering followed by carefully controlled thermal oxidation. This method is known to give high quality compact thin films with uniform high deposition rates. Thin films deposited on both bare glass and indium tin-oxide (ITO) coated glass substrates were studied, respectively, as passive and active thermochromic devices for their electrical and optical switching behaviors. Thin films varying in thicknesses from 65 to 250 nm were investigated. ITO film was used as an integrated heating device to activate the phase transition via an applied bias voltage. Such structures were found to bear several advantages from an application point of view.     

Comparative study between silicon-rich oxide films obtained by LPCVD and PECVD

A comparative study of compositional and optical properties of silicon-rich oxide (SRO) films deposited by low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD) is presented. Infrared spectra revealed the presence of hydrogen bonded to silicon atoms in the SRO–PECVD films, whereas in SRO–LPCVD films the IR spectra looked like the stoichiometric thermal silicon oxide. Moreover, X-ray photoelectron spectroscopy (XPS) studies showed that the SRO–PECVD films contain a higher content of nitrogen than SRO–LPCVD films. In spite of differences, the SRO films obtained by both methods show a strong room-temperature photoluminescence (PL). However, the highest PL intensity was emitted by SRO films obtained by LPCVD.     

Optical band gap of zinc nitride films prepared on quartz substrates from a zinc nitride target by reactive rf magnetron sputtering

Polycrystalline zinc nitride films have been synthesized onto quartz substrates from the zinc nitride target and the nitrogen working gas by reactive rf magnetron sputtering at room temperature. X-ray diffraction study indicates that polycrystalline zinc nitride films are of cubic structure with the lattice constant a = 0.979(1) nm and have preferred orientations with (3 2 1) and (4 4 2). Its absorption coefficients as well as the film thickness are calculated from the transmission spectra, which are measured with a double beam spectrophotometer. The optical band gap has been determined from the photon energy dependence of absorption coefficient, an indirect transition optical band gap of 2.12(3) eV has been obtained.     

Condensation Surface Temperature as a Means for Studying Film Formation Mechanisms

A rise in the condensation surface temperature during film growth is a result of energy dissipation on the condensation surface. An example of energy dissipation is the dissipation of chemical reaction heat, which releases during film deposition by reactive magnetron sputtering. The monitoring of the surface temperature during TiN film deposition by reactive (Ti–in–N₂) and nonreactive (TiN–in–Ar or TiN–in–N₂) sputtering methods has shown that this temperature is higher in the reactive case and decreases in the (TiN–in–Ar)–(TiN–in–N₂) sequence of nonreactive sputtering modifications. It has been found that the composition and crystal structure of TiN films do not depend on the growth method and are identical to those of bulk titanium nitride. Based on these results, a formation mechanism of films obtained by the above methods has been suggested. In the case of reactive sputtering, the film was supposed to grow on the condensation surface through a reaction between titanium and nitrogen atoms. In the cases of nonreactive sputtering, the film forms from TiN molecules.     

Surface partition of ion energy during the growth of TiNx thin films

A simple evaluation of ion-deposited energy during surface displacement of adatoms has been presented for physical vapor deposition technology using an appropriate interaction model. The rf reactive magnetron sputtering deposition of titanium nitride (TiN_x) thin films was taken as evidence supporting the theoretical calculation. The evolution of crystallite morphology dependent on bias (or input power) illustrates that surface and subsurface microstructure of growing films can be optimized by increasing the mobility of adatoms through ion-assistance.     

Surface characterization of TiO2 thin films obtained by high-energy reactive magnetron sputtering

This paper presents the results of surface characterization of TiO₂ thin films deposited on different substrates by the use of high-energy reactive magnetron sputtering. Structural investigations carried out by X-ray diffraction (XRD) and atomic force microscopy (AFM) have shown a strong influence of both the substrate type, and its placement in the deposition chamber (relative to the sputtering target), on the structural properties of the films. In all cases, there is evidence for pseudoepitaxial growth. XRD examination showed existence of TiO₂-rutile phase with preferred (1 1 0) orientation and AFM measurements revealed nanocrystalline structure directly after deposition. X-ray photoelectron spectroscopy analysis showed that the TiO₂ films have stoichiometric composition.     

Thermochromic VO2 thin films synthesized by rf-inverted cylindrical magnetron sputtering

The novel physical vapor deposition called inverted cylindrical magnetron sputtering (also known as hollow cathode sputtering) is commonly used to coat wires, fibers, ribbons as well as all sides of three-dimensional substrates. It is a reproducible method for the production of nano-structured systems onto complex shapes substrates. This paper reports the first synthesis and feasibility of reliably reproduced stoichiometric pure textured VO₂ nano-structures by the rf-inverted cylindrical magnetron sputtering. Morphological, structural, elemental analysis and optical properties of synthesized VO₂ under optimized conditions are reported.     

Electrophysical properties of dielectric films in MDM-structures

Using the methods of reactive cathode sputtering in a low-voltage, penning-discharge installation, dielectric films from silica, silicon nitride, aluminum nitride, etc. are obtained. Parameters of the films in MDM structures, their optical properties and porosity are investigated as a function of the deposition rate, substrate temperature and reaction gas pressure. It is found out that the films from silicon nitride exhibit the highest dielectric strength and those from silicon dioxide show the least dielectric loss.     

Effect of balanced and unbalanced magnetron sputtering processes on the properties of SnO2 thin films

A comparative study has been carried on the role of balanced magnetron (BM) and unbalanced magnetron (UBM) sputtering processes on the properties of SnO₂ thin films. The oxygen partial pressure, substrate temperature and deposition pressure were kept 20%, 700 °C and 30 mTorr, respectively and the applied RF power varied in the range of 150–250 W. It is observed that the UBM deposition causes significant effect on the structural, electrical and optical properties of SnO₂ thin films than BM as evidenced by X-ray diffraction, C-V, Spectroscopic Ellipsometer and Photoluminescence measurements. The value of band gap (E_g) of the films deposited at 150 W in UBM is found as E_g = 3.83 eV which is much higher than the value of E_g = 3.69 eV as observed in BM sputtering indicating that UBM sputtering results in good crystalline quality. Further, the C-V measurements of SnO₂ thin films deposited using UBM at high power 250 W show hysteresis with large flat band shift indicating that these thin films can be used for the fabrication of memory device. The observed results have been attributed to different mechanisms which exist simultaneously under unbalanced magnetron sputtering due to ion bombardment of growing SnO₂ thin film by energetic Ar+ ions.     

氮化钛薄膜的光学性能分析

利用磁控溅射法，在不同的工艺条件下制备氮化钛薄膜。详细分析了不同工艺条件下薄膜的光谱选择特性以及相应的光学常数，通过俄歇电子能谱对薄膜的不同深度的元素成分进行了分析，由原子力显微镜测量并处理得到氮化钛薄膜的表面形貌图。结果表明，氮化钛薄膜的光学性能严格依赖于氮和钛原子数比，符合化学计量比的TiN薄膜具有良好的光谱选择性。基底加负偏压溅射可进一步改善薄膜的性能。     

Photoluminescence properties of SiNx/Si amorphous multilayer structures grown by plasma-enhanced chemical vapor deposition

Very thin (nanometric) silicon layers were grown in between silicon nitride barriers by SiH₂Cl₂/H₂/NH₃ plasma-enhanced chemical vapor deposition (PECVD). The multilayer structures were deposited onto fused silica and silicon substrates. Deposition conditions were selected to favor Si cluster formation of different sizes in between the barriers of silicon nitride. The samples were thermally treated in an inert atmosphere for 1 h at 500 °C for dehydrogenation. Room-temperature photoluminescence (RT-PL) and optical transmission in different ranges were used to evaluate the optical properties of the structures. UV-VIS absorption spectra present two band edges. These band edges are well fitted by the Tauc model typically used for amorphous materials. RT-PL spectra are characterized by strong broad bands, which have a blue shift as a function of the deposition time of the silicon layer, even for as-grown samples. The broad luminescence could be associated with the confinement effect in the silicon clusters. After annealing of the samples, the PL bands red shift. This is probably due to the thermal decomposition of N-H bonds with further effusion of hydrogen and better nitrogen passivation of the nc-Si/SiN_x interfaces.     

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.     

Thick c-BN films deposited by radio frequency magnetron sputtering in argon/nitrogen gas mixture with additional hydrogen gas

The excellent physical and chemical properties of cubic boron nitride(c-BN) film make it a promising candidate for various industry applications. However, the c-BN film thickness restricts its practical applications in many cases. Thus, it is indispensable to develop an economic, simple and environment-friend way to synthesize high-quality thick, stable c-BN films. High-cubic-content BN films are prepared on silicon(100) substrates by radio frequency(RF) magnetron sputtering from an h-BN target at low substrate temperature. Adhesions of the c-BN films are greatly improved by adding hydrogen to the argon/nitrogen gas mixture, allowing the deposition of a film up to 5-μm thick. The compositions and the microstructure morphologies of the c-BN films grown at different substrate temperatures are systematically investigated with respect to the ratio of H_2 gas content to total working gas. In addition, a primary mechanism for the deposition of thick c-BN film is proposed.