Copper nitride films deposited by dc reactive magnetron sputtering

Copper nitride (Cu₃N) films were deposited on glass substrates by sputtering of copper target under various substrate temperatures in the range 303–523 K using dc reactive magnetron sputtering. The substrate temperature highly influenced the structural, mechanical, electrical and optical properties of the deposited films. The X-ray diffraction measurements showed that the films were of polycrystalline nature and exhibit preferred orientation of (111) phase of Cu₃N. The microhardness of the films increased from 2.7 to 4.4 GPa with the increase of substrate temperature from 303 to 473 K thereafter decreased to 4.1 GPa at higher temperature of 523 K. The electrical resistivity of the films decreased from 8.7 × 10⁻¹ to 1.1 × 10⁻³ Ωcm and the optical band gap decreased from 1.89 to 1.54 eV with the increase of substrate temperature from 303 to 523 K respectively.     

In-situ electrical characterization of ultrathin TiN films grown by reactive dc magnetron sputtering on SiO2

Ultrathin TiN films were grown by reactive dc magnetron sputtering on thermally oxidized Si (100) substrates. The electrical resistance of the films was monitored in-situ during growth in order to determine the minimum thickness of a continuous film. The coalescence thickness has a minimum of 1 nm at a growth temperature of 400 °C after which it increases with growth temperature. The minimum thickness of a continuous film decreases with increasing growth temperature from 2.9 nm at room temperature to 2.2 nm at 650 °C. In-situ resistivity measurements show that films grown at 500 °C and above are resistant to oxidation indicating high density. X-ray photoelectron spectroscopy and X-ray diffraction measurements show that the TiN grain stoichiometry and grain size increases with increasing growth temperature.     

Structural characterization of ZnO thin films deposited by dc magnetron sputtering

In this work we present recent results on ZnO thin films grown by dc magnetron sputtering technique at room temperature (RT), focusing on structural and surface characterization using conventional cross-section transmission electron microscopy (XTEM) and high resolution cross section transmission electron microscopy (HRXTEM) in an attempt to understand the thickness influence on film, mechanical and optical properties as well as photoreduction/oxidation conductivity changes. Films were found to be polycrystalline with a columnar mode of growth. For films with thickness over 100 nm, XTEM and HRTEM analysis evidenced the presence of a small grains transition layer near interface with the substrate, feature which plays an important role in ZnO thin films for gas sensing application. The control of such structural parameters is proved to be critical for the improvement of their gas sensing performance.     

Characterization of CuAlO2 films prepared by dc reactive magnetron sputtering

Thin films of copper aluminum oxide (CuAlO₂) were prepared on glass substrates by dc magnetron sputtering at a substrate temperature of 523 K under various oxygen partial pressures in the range 1 × 10⁻⁴–3 × 10⁻³ mbar. The dependence of cathode potential on the oxygen partial pressure was explained in terms of oxidation of the sputtering target. The influence of oxygen partial pressure on the structural, electrical and optical properties was systematically studied. p-Type CuAlO₂ films with polycrystalline nature, electrical resistivity of 3.1 Ω cm, Hall mobility of 13.1 cm² V⁻¹ s⁻¹ and optical band gap of 3.54 eV were obtained at an oxygen partial pressure of 6 × 10⁻⁴ mbar.     

Thermochromic properties of vanadium oxide films prepared by dc reactive magnetron sputtering

A transparent vanadium oxide film has been one of the most studied electrochromic (EC) and Thermochromic (TC) materials. Vanadium oxide films were deposited at different substrate temperatures up to 400 °C and different ratios of the oxygen partial pressure (P_O2). SEM, AFM and X-ray diffraction's results show detail structure data of the films. IR mode assignments of the films measured by IR reflection-absorbance in NGIA (near grazing incidence angle) are given. It is found that the film has V₂O₅ and VO₂ combined structures. The films exhibit clear changes in transmittance when the environment temperature (T_e) is varied, especially in the 3600-4000 cm^− 1 range. Applying a T_e that is higher than a critical temperature (T_c) to the samples, the as-RT (room temperature) deposited film with 9% P_O2 has a transmittance variation of 30%, but the films that were deposited on a heated substrate of 400 °C have little variation. There is tendency of bigger variation in transmittance for the sample deposited at a larger P_O2, when it is applied by 200 °C T_e.     

Electronic properties of n-ZnO(Al)/p-Si heterojunction prepared by dc magnetron sputtering

The electronic properties of the interface between p-type Si and Al-doped ZnO have been investigated. Films of ZnO(Al) with a thickness of 300 nm were deposited at room temperature by dc magnetron sputtering and subsequently subjected to heat treatment in air in the temperature range 100-400 °C. Current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements were used to characterize the electrical properties of the heterostructure. The I-V measurements show a diode-like behavior with a rectification of ~ 3-4 orders of magnitude. However, annealing above 200 °C gives rise to a pronounced recombination/generation current in the depletion region, which correlates with an increase of the carrier concentration close to the interface and indicates defect formation. Indeed, DLTS reveals the presence of two prominent defect states, one at 0.38 eV above the valence band edge (E_v), and the other, formed during the heat treatment above 250 °C, around E_v + 0.43 eV, which is consistent with the I-V and C-V data.     

反应磁控溅射沉积氧化铜薄膜及其电化学性能研究

以金属铜为靶材,氧气为反应气体,采用射频磁控溅射法在不同温度的不锈钢基片上制备了氧化铜薄膜电极.采用X射线衍射(XRD)和原子力显微镜(AFM)分别对薄膜的组成和形貌进行了表征分析.电化学测试表明,在基片温度为室温条件下沉积得到的薄膜电极比300℃基片温度沉积得到的薄膜电极首次放电容量高,达到785μAh/(cm2·μm),但循环100次后后者放电容量较高.用交流阻抗法测得锂离子在氧化铜薄膜中的扩散系数为2.46×10-15cm2/s.     

Investigation on Mn doped ZnO thin films grown by RF magnetron sputtering

In this paper, we have investigated the Zn_1 − x Mn_xO (x = 0.05, 0.10 and 0.15) thin films grown by RF magnetron sputtering. The grown films on sapphire [Al₂O₃(0001)] substrates have been characterized using X-ray Diffraction (XRD), Photoluminescence (PL) and Vibrating Sample Magnetometer (VSM) in order to investigate the structural, optical and magnetic properties of the films respectively. It is observed from XRD that all the films are single crystalline with (002) preferential orientation along c-axis. PL spectra reveal that the addition of Mn marginally shifts the Near Band Edge (NBE) position towards the higher energy side. The magnetic measurements of the films using VSM clearly indicate the ferromagnetic nature.     

Thickness dependent properties of nickel oxide thin films deposited by dc reactive magnetron sputtering

Nickel oxide thin films of various thicknesses were grown on glass substrates by dc reactive magnetron sputtering technique in a pure oxygen atmosphere with sputtering power of 150 W and substrate temperature of 523 K. Crystalline properties of NiO films as a function of film thickness were investigated using X-ray diffraction. XRD analysis revealed that (200) is the preferred orientation and the orientation of the films changed from (200) to (220) at film thickness of 350 nm. The maximum optical transmittance of 60% and band gap of 3.82 eV was observed at the film thickness of 350 nm. The lowest electrical resistivity of 5.1 Ω cm was observed at a film thickness of 350 nm, thereafter resistivity increases with film thickness.     

Study on ZnO thin films deposited on sol-gel grown ZnO buffer by RF magnetron sputtering

ZnO thin films with preferential C-orientation and dense microstructure have been prepared using RF magnetron sputtering method by the insertion of a sol-gel grown ZnO buffer layer. The XRD results show that the C-orientation of the film deposited on ZnO buffer is obviously better than that deposited directly on lime-glass substrate. With an increase of the RF power from 100 to 380 W, C-orientation of the films with ZnO buffer improves and the grain size increases. When the RF power equals 550 W, the orientation of the film changes to (1 0 0) and the grain size decreases. The crystalline and microstructure quality of the films can be improved after annealing, however, the grain size is not much dependent on the annealing temperature in the range of 560-610 °C.     

Optical and structural characteristics of ZnO thin films grown by rf magnetron sputtering

Nanostructured ZnO thin films on Pyrex glass substrates were deposited by rf magnetron sputtering at different substrate temperatures. Structural features and surface morphology were studied by X-ray diffraction and atomic force microscopy analyses. Films were found to be transparent in the visible range above 400 nm, having transparency above 90%. Sharp ultraviolet absorption edges around 370 nm were used to extract the optical band gap for samples of different particle sizes. Optical band gap energy for the films varied from 3.24 to 3.32 eV and the electronic transition was of the direct in nature. A correlation of the band gap of nanocrystalline ZnO films with particle size and strain was discussed. Photoluminescence emission in UV range, which is due to near band edge emission is more intense in comparison with the green band emission (due to defect state) was observed in all samples, indicating a good optical quality of the deposited films.     

沉积时间对磁控反应溅射制备TiO2薄膜性能的影响

应用直流磁控反应溅射法,在玻璃基体上制备了具有光催化活性的TiO2薄膜.TiO2薄膜的厚度随沉积时间的增加而均匀增长.基体温度则在溅射的最初1h很快上升到110℃,溅射7h基体温度不超过130℃.溅射2h得到的是非晶态TiO2薄膜,而溅射3～7h制备的薄膜为锐钛矿型结构.非晶态和小晶粒TiO2薄膜的紫外一可见透射光谱谱带边沿与结晶较好的TiO2薄膜相比有明显的蓝移,薄膜的透射率随沉积时间的增加而下降.钛以四价钛的形式存在于TiO2薄膜中.TiO2薄膜的光催化活性随沉积时间争薄膜厚度的增加而有较大提高.     

Characterization of inhomogeneity in TiO2 thin films prepared by pulsed dc reactive magnetron sputtering

This article discusses an analytical method for characterizations of TiO₂ thin films and determinations of the degree of their inhomogeneity. The TiO₂ films were prepared by a pulsed dc magnetron sputtering with an operating pressure as a main experimental parameter. The obtained films were primarily characterized for film crystallinity, microstructures and optical properties by spectroscopic ellipsometry. The measured ellipsometric data were analyzed by the single-, the double, and the triple-layer models in order to match with the inhomogeneous film structure proposed in the Thornton structure zone model. The results were then compared with those obtained from grazing-incidence X-ray diffraction, field-emission scanning electron microscopy and high-resolution transmission electron microscopy. The study revealed that the pulsed dc sputtered TiO₂ films could be best described by the inhomogeneous triple-layer physical model. Although the films deposited at lower operating pressure had a dense structure with a mirror-like surface topography, the films deposited at higher operating pressure had the porous structure with the rough surface and the void.     

Electrical and optical properties of ZnO:Al thin films grown by magnetron sputtering

The properties of transparent conductive ZnO:Al thin films grown by R.F. magnetron sputtering method are investigated. The working pressure (argon gas) is changed from 2.5 to 40.0 mTorr to study its influence on the characteristics of ZnO:Al thin films. The ZnO:Al thin films have better texture due to the increase in the surface mobility, which resulted from the increase in the mean free path of sputtering gas under lower working pressure. The microstructure of ZnO:Al films is found to be affected obviously by changing the working pressure. It is shown that the grain size of ZnO:Al thin films decreases with the increase of working pressure. The X-ray diffraction patterns indicate that the poor crystallized structure of ZnO:Al films is obtained at higher working pressure. Except 40 mTorr, the highly (002)-oriented ZnO:Al thin films can be found at the measured range of working pressure. Moreover, the growth rate of the films decreases from 1.5 to 0.5 nm/min as the working pressure increases from 2.5 to 40.0 mTorr. The results of optical transmittance measurement of ZnO:Al thin films reveal a high transmittance (>80%) in visible region and exhibit a sharp absorption edge at wavelength about 350 nm.     

A comparative study of CrNx coatings Synthesized by dc and pulsed dc magnetron sputtering

Chromium nitride (CrN_x) coatings were prepared by reactively sputtering chromium metal target with various nitrogen flow rate percentages (f_N2) using a closed field unbalanced magnetron sputtering system operated in dc and middle frequency pulsed condition (100 kHz and 50% duty cycle). In this study, plasma examination proved that a large amount of ions with a wide range of ion energies (up to 65 eV and mainly from 10-30 eV region) was identified in the pulsed plasma compared to the low ion flux and energy (0-10 eV) in a dc discharged plasma. The results showed that the phase structure of CrN_x coatings was changed from nitrogen doped Cr(N) to pure β-Cr₂N, and to a mixture of β-Cr₂N and c-CrN and then to pure c-CrN phases with an increase in the f_N2 in both dc and pulsed conditions. However, the pulsed CrN_x coatings exhibit lower N concentrations than dc CrN_x coatings prepared under the same f_N2, which leads to the existing of β-Cr₂N phase within a wide range of f_N2 (30-50%). In comparison with the typical large columnar structure in the dc sputtered coatings, the pulsed CrN_x coatings exhibit dramatic microstructure improvements which benefited from the improved plasma density and ion bombardment from the pulsed plasma, where the super dense and nearly equi-axial structures were observed in a wide range of f_N2. The microstructure improvements contributed to the enhancements in the hardness and wear resistance of pulsed CrN_x coatings. In the pulsed CrN_x coatings, the hardness values were above 30 GPa when the f_N2 is in the range of 30-40%, which is related to the formation of the β-Cr₂N phase. With the formation of a mixture of β-Cr₂N and c-CrN phases in the coatings deposited with 40-50% f_N2, a low COF of 0.36 and wear rate of 1.66 × 10^− 6 mm³ N^− 1 m^− 1 can be achieved.     

Effect of sublayer surface treatments on ZnO transparent conductive oxides using dc magnetron sputtering

Novel sublayer surface treatments were investigated to improve the conductivity of aluminum-doped zinc oxide (ZnO:Al) fabricated by using dc magnetron sputtering on a glass substrate. Introducing artificial minute flaws on the surface of glass substrates enhanced the crystallinity of ZnO:Al films and decreased the resistivity accompanying the increase of electron mobility. Combination of the surface treatment and sputter beam control, i.e., interruption of high-energy oxygen with shadow masks, further reduced the resistivity of the film to 3.7 × 10^− 4 Ω cm (thickness 70 nm).     

反应磁控溅射的进展

反应磁控溅射被广泛应用于制备化合物薄膜。本文分析了反应磁控溅射中迟滞效应、靶中毒与打火现象,讨论了提高反应磁控溅射沉积速率、抑制靶面打火与保持溅射过程稳定性的途径。在阐述了近年来反应磁控溅射量新研发进展的基础上,介绍了中频溅射在减反膜、高反膜和低辐射率膜工业化生产中的应用。     

高频半桥直流磁控溅射电源设计

稳定可靠的直流电源是直流磁控溅射镀膜质量的关键,本文采用开关频率为50 kHz的半桥拓扑,对主回路结构和参数进行设计.以SG3525控制芯片为核心,对控制回路按小信号模型建模,使用PI补偿网络,通过电阻负载实验得到稳定的直流.     

Strain evolution in heteroepitaxial ZnO/sapphire(0001) thin films grown by radio frequency magnetron sputtering

We present the strain evolution of ZnO/sapphire(0001) thin films studied by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The effect of input radio frequency (rf) sputtering power and growth temperature was examined. Initially the highly strained flat ZnO layers were grown. At samples deposited at higher temperatures than ∼ 500 °C, the strain was fully relaxed by nucleating the ZnO nano-grains as the film thickness increased. However, we found that the strain was partially relaxed at the samples grown at lower temperatures, which was attributed to the insufficient surface undulations. For the effect of rf input power, a consistent behavior of strain relaxation independent of the rf input power was observed. The ZnO nano-grains were enlarged and transformed to well-defined hexagonal nano-discs with film thickness.