Properties of silicon nitride thin films obtained by reactive sputtering

The dependence of the properties of Si₃N₄ films on the reactive sputtering parameters and changes of the electrical properties during long term aging in air were investigated. It was found that the properties, content and structure of films produced by the reactive sputtering of silicon in Ar-N₂ mixtures can vary widely depending on the technological parameters.     

Characterization of tin oxide thin films deposited by reactive sputtering

SnO_x Thin films deposited by reactive sputtering are characterized by conversion electron Mössbauer spectroscopy, X-ray diffraction, nuclear resonant scattering and Rutherford backscattering analyses and sheet resistance measurements. The samples were submitted to thermal annealing and exposed to butane gas. The highly disordered as-deposited thin film is modified under thermal processing and gas exposure, changing the oxygen vacancy concentration. This behaviour should affect the steady state response of tin oxide sensors.     

Properties of zirconia thin films prepared by reactive magnetron sputtering

The search for alternative dielectric materials with high dielectric constant, thermodynamic stable on silicon substrate and low direct tunneling current leads to oxide based materials like zirconia. Zirconia thin films were prepared by reactive magnetron sputtering. The capacitance voltage, ac and dc electrical characteristics were investigated and the values like fixed oxide charges were calculated and compared among the samples with and without annealing. Films annealed at 700 °C showed a dielectric constant ∼ 26 with interface trap densities of 1.629 × 10¹² eV^− 1 cm^− 2.     

Thermopower measurements on SiO x thin films

Thermopower and d.c. electrical conductivity measurements have been carried out between 125 and 625 K on SiO _x thin films, 130 nm thick, deposited on to Corning 7059 substratesin vacuo 1 mPa at 1.5 nm sec^–1. The thermopower, d.c. conductivity and their respective activation energies are fitted to a polynomial expression in 1/T. Below 400 K, the thermopower is negative, at 400 K the thermopower activation energy is approximately zero and the dominant current carriers are holes at the valence band edge, between 400 and 470 they are polaronic holes, between 470 and 590 K non-polaronic holes, and above 590 K electrons. Energy band diagrams are proposed for each temperature range studied.     

Dielectric oxynitride LaTiOxNy thin films deposited by reactive radio-frequency sputtering

LaTiO_xN_y thin films have been deposited by RF sputtering on (001) Nb-doped SrTiO₃ and (001) MgO single-crystalline substrates at high temperature (T_S = 800 °C) under different nitrogen ratios in the plasma (vol.% N₂ = 0, 25, 71). The band gaps ranged from E_g = 3.30 eV for the epitaxial transparent film containing no nitrogen to E_g = 2.65 eV for the textured coloured film containing a moderate amount of nitrogen. Dielectric characterization in the frequency range [100 Hz-1 MHz], using a metal-insulator-metal structure, has shown a stable permittivity and loss tangent of the epitaxial low-nitrided LaTiO_xN_y film with values of ε′ = 135 and tanδ = 1.2 10^− 2 at 100 kHz (RT).     

磁控溅射制备ZnO:Eu薄膜发光性能研究

采用射频磁控溅射法在蓝宝石基片上制备ZnO:Eu薄膜,通过X射线衍射仪和荧光分光光度计等测试其晶体结构和发光特性,分析退火对薄膜晶体结构和发光特性的影响.结果表明,ZnO:Eu薄膜为C轴择优生长的多晶薄膜,实现ZnO基质中掺杂Eu3+;退火样品结晶质量较好,有助于ZnO:Eu薄膜中Eu3+的5D0-7F2的能级跃迁发光;高于ZnO带隙的高能激发(间接激发)和Eu3+的7F0-5L6和7F3-5D2能级间的低能共振激发(直接激发)都能观察到Eu3+的5D0-7F2能级跃迁的特征发光(618nm);间接激发时存在ZnO基质与Eu3之间发生能量传递.     

Electrochromic behavior of W(x)Si(y)O(z) thin films prepared by reactive magnetron sputtering at normal and glancing angles

This work reports the synthesis at room temperature of transparent and colored W(x)Si(y)O(z) thin films by magnetron sputtering (MS) from a single cathode. The films were characterized by a large set of techniques including X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), Fourier transform infrared (FT-IR), and Raman spectroscopies. Their optical properties were determined by the analysis of the transmission and reflection spectra. It was found that both the relative amount of tungsten in the W-Si MS target and the ratio O(2)/Ar in the plasma gas were critical parameters to control the blue coloration of the films. The long-term stability of the color, attributed to the formation of a high concentration of W(5+) and W(4+) species, has been related with the formation of W-O-Si bond linkages in an amorphous network. At normal geometry (i.e., substrate surface parallel to the target) the films were rather compact, whereas they were very porous and had less tungsten content when deposited in a glancing angle configuration. In this case, they presented outstanding electrochromic properties characterized by a fast response, a high coloration, a complete reversibility after more than one thousand cycles and a relatively very low refractive index in the bleached state.     

Microstructure evolution and photoluminescence in nanocrystalline Mg(x)Zn(1 - x)O thin films

The effects of Mg concentration and annealing temperature on the characteristics of nanocrystalline Mg(x)Zn(1 - x)O thin films (where x = 0-0.4) were studied using electron microscopy and photoluminescence. The films were prepared by a sol-gel method. The solid solubility limit of MgO in ZnO for the sol-gel-derived Mg(x)Zn(1 - x)O films in the present study was determined to be ～ 20 at.%. Microstructural characterization of the films showed that the wurtzite crystallites decrease in size with increase in Mg concentration up to the solubility limit. Increasing Mg concentration beyond the solubility limit resulted in a decrease in crystallinity of the films. The bandgap energy was found to increase with Mg concentration whereas the linewidth first increased and then decreased when the Mg concentration was increased beyond the solubility limit. Photoluminescence properties have been correlated to the microstructure of the films. A growth mechanism for Mg(x)Zn(1 - x)O nanocrystalline films under the present processing conditions has also been proposed.     

Preparation of Cr(N,O) thin films by RF reactive unbalanced magnetron sputtering

Chromium oxynitride thin films were deposited by radio-frequency (RF) reactive unbalanced magnetron sputtering at various O₂ flow rates onto Si(100) and glassy carbon substrates. The compositions of the thin films were analyzed by Rutherford backscattering spectroscopy. The thin films were found to contain up to 44 at.% oxygen. In Fourier-transform infrared spectra, a peak attributed to the Cr-N bond of CrN was observed, but no peak attributable to the Cr-O bond of Cr₂O₃ was found. The textures of the thin films were observed by transmission electron microscopy, which revealed that samples had a columnar structure. The hardness of the thin films was measured by nanoindentation. The hardness increased from 20 GPa to a maximum value of 31 GPa with increasing oxygen content.     

Water as reactive gas to prepare titanium oxynitride thin films by reactive sputtering

Thin films of titanium oxynitride were successfully prepared by dc reactive magnetron sputtering using a titanium metallic target, argon, nitrogen and water vapour as reactive gases. The nitrogen partial pressure was kept constant during every deposition whereas that of the water vapour was systematically changed from 0 to 0.1 Pa. The evolution of the deposition rate with an increasing amount of water vapour injected into the process was correlated with the target poisoning phenomenon estimated from the target potential. Structure and morphology of the films were analysed by X-ray diffraction and scanning electron microscopy. Films were poorly crystallised or amorphous with a typical columnar microstructure. Nitrogen, oxygen and titanium concentrations were determined by Rutherford backscattering spectroscopy and nuclear reaction analysis, and the amount of hydrogen in the films was also quantified. Optical transmittance in the visible region and electrical conductivity measured against temperature were gradually modified from metallic to semiconducting behaviour with an increasing supply of the water vapour partial pressure. Moreover, an interesting maximum of the electrical conductivity was observed in this transition, for a small amount of water vapour.     

Characterization of iridium oxide thin films deposited by pulsed-direct-current reactive sputtering

Thin films of iridium oxide were deposited on silicon and borosilicate glass substrates by pulsed-direct-current (pulsed-DC) reactive sputtering of iridium metal in an oxygen-containing atmosphere. Optimum deposition conditions were identified in terms of plasma pulsing conditions, oxygen partial pressures, and substrate temperature. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and Rutherford backscattering spectroscopy. According to the results, it was possible to obtain films that are near-stoichiometric, smooth and uniform in texture. The films deposited without substrate heating were amorphous, and those deposited at substrate temperatures above 300 °C were found to have a homogeneous polycrystalline structure. The results also showed that pulsed-DC sputtered iridium oxide films were smoother and had lower micro-inclusions density than DC-sputtered films obtained under otherwise similar deposition conditions. This improvement in the film quality is at the expense of a tolerable decrease in the deposition rate.     

反应RF磁控溅射法制备非晶氧化硅薄膜及其特性研究

在氧气和氩气的混合气体中,在没有额外加热的条件下用反应射（RF）溅射硅靶制备了非晶氧化硅（a-SiO2)薄膜,并测试分析了薄膜的结构和电特性与O2／Ar流量比的关系。当固定氩气流量,改变氧气流量时,薄膜沉积速率先急剧减少,再增大,然后又减少。当O2／Ar≥0．075时,得到满足化学配比的氧化硅薄膜。并且,随着O2／Ar流量比的增大,薄膜的电阻,电场击穿强度都有所增大,而在HF缓冲溶液（BHF）中的腐蚀速率下降,所有的样品中无明显的H－OH水分子的红外吸收峰。比较发现反应射频（RF）磁控溅射法制备的a-SiO2薄膜具有良好的致密性和绝缘性。     

The growth of indium-tin-oxide thin films on glass substrates using DC reactive magnetron sputtering

The growth of indium-tin-oxide thin films as a function of thickness using DC reactive magnetron sputtering was investigated. As the film thickness grew, the crystallinity increased showing both (2 2 2) and (4 0 0) planes. However, the peak intensity ratio of I₂₂₂/I₄₀₀ in the X-ray diffraction pattern decreased with the thickness, implying a preferred orientation along the (4 0 0) planes at the higher thickness. The grain sizes and domain boundaries grew clearly and the specific resistivities decreased with the film thickness. Two components of the specific resistivities, carrier mobility and carrier concentration, showed opposite behaviour: (i) increasing carrier concentration; (ii) decreasing carrier mobility with increase in the film thickness. Furthermore, the graded growth of the ITO thin film could also be shown from the optical properties and morphological properties by UV/Vis/NIR spectroscopy and scanning electron microscopy.     

Properties of TaSiN thin films deposited by reactive radio frequency magnetron sputtering

TaSiN is a promising material for application as electrically conductive diffusion barrier for the integration of high permittivity perovskite materials in integrated circuits. TaSiN thin films were deposited by reactive radio frequency magnetron sputtering using TaSi and TaSi_2.7 targets in an Ar/N₂ atmosphere. The sputter power was varied in order to achieve different TaSiN compositions. The stoichiometry of as-deposited films was estimated using Rutherford backscattering spectroscopy. The as-deposited TaSiN thin films are amorphous. Their crystallization temperature is above 700 °C and increases with higher nitrogen content. They have metallic conduction and ohmic behavior. The resistivity of as deposited films is in the range from 10^− 6 Ω m up to 10^− 3 Ω m and increases with nitrogen content. It was found that p⁺⁺-Si/Ta₂₁Si₅₇N₂₁ develops unacceptable high contact resistance. Introducing an intermediate Pt layer the stack p⁺⁺-Si/Pt/Ta₂₁Si₅₇N₂₁ had a good conductive properties and good thermal stability at 700 °C.     

ZnO thin films with DC and RF reactive sputtering

ZnO thin films were deposited onto glass substrates with direct current or radio frequency reactive magnetron sputtering process from a Zn target. All films demonstrated strong (002) preferential orientation. It was also observed that the type of plasma excitation, oxygen partial pressure, bias, working distance and doping could significantly change the microstructure, crystallinity and deposition rate of the films. The mechanisms governing these changes were briefly discussed.     

Effects of oxygen percentage on the growth of copper oxide thin films by reactive radio frequency sputtering

Copper oxide thin films were deposited onto glass substrates by reactive radio frequency magnetron sputtering at various oxygen percentage flow rates R(O₂). X-ray diffraction analysis revealed that nanocrystallite copper oxide thin films with cubic, tetragonal, and monoclinic structure were formed at R(O₂) values of 10%, 20%, and ≥30%, respectively. Energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy were used to verify the copper oxides phases. With increased R(O₂), the root mean square surface roughness of the deposited films decreased from 4.82 nm to 1.78 nm. Moreover, both the band gap type and value changed with increased R(O₂). For R(O₂) at 20%, single phase tetragonal Cu₄O₃ thin film with a direct band gap of 2.20 eV was formed. For R(O₂) ≥ 30%, single phase monoclinic CuO thin films with an indirect band gap of 1.20 eV–1.25 eV were formed. In addition, conductive copper oxide thin films tended to form for R(O₂) < 30%, whereas insulator oxide thin films tended to form for R(O₂) ≥ 30%. Through this study, the crystallization behavior, the band gap, and the resistivity properties of the deposited copper oxide thin films as a function of the R(O₂) were obtained.     

Sm3+ photoluminescence in co-sputtered SiO2 thin films

Thin films of SiO₂ containing Sm were deposited by magnetron co-sputtering. The concentration of Sm in the films was varied by changing the amount of Sm placed on the fused silica target. The samarium content in the films was established by Rutherford back-scattering measurements. Photoluminescence (PL) was excited with the 488-nm line of an Ar ion laser. It consists of several lines in the visible, which are assigned to transitions between multiplets of Sm³⁺. The concentration dependence of the PL intensity was studied. It passes through a maximum and decreases at higher Sm content. The films were annealed in vacuum at temperatures between 300 and 1000 °C. There was a strong increase in the PL intensity after annealing at 600 °C, and then it fell again after annealing at 1000 °C. The data are compared to spectra of Sm³⁺ in other matrices. The mechanisms of PL excitation and quenching are discussed.