Diamond/graphite content and biocompatibility of DLC films fabricated by PLD

Biocompatibility and physicochemical properties of diamond-like carbon (DLC) thin layers prepared by pulsed laser deposition method were studied. The films of high and low diamond/graphite content were prepared by changing the laser energy density on the graphite target from 4 to 11 J cm⁻². The bonds and surface properties as roughness, atomic force microscopy topology, contact angle parameters, and zeta potential were measured. The cell adhesion/proliferation on DLC layers was tested using normal human fibroblasts and keratinocytes.     

Field emission properties of DLC and phosphorus-doped DLC films prepared by electrochemical deposition process

Field emission behavior of diamond-like carbon (DLC) and phosphorus-doped DLC (p-DLC) films prepared by electrochemical deposition process was comparatively investigated. It was shown phosphorus incorporation in the DLC film could lower the turn on field from 12 to 9.5 V/μm and increase the current density from 12.6 to 45.7 μA/mm² under high electric field. And better field emission performance of p-DLC films would be mainly attributed to the influence of the surface morphology and the changes of microstructure due to the phosphorus incorporation.     

Investigation of properties of Cu containing DLC films produced by PECVD process

Copper containing diamond like carbon (Cu-DLC) thin films were deposited on various substrates at a base pressure of 1×10^?3 Torr using a hybrid system involving DC-sputtering and radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) techniques. The compressive residual stresses of these films were found to be considerably lower, varying between 0.7 and 0.94 GPa and Cu incorporation in these films improve their conductivity significantly. Their structural properties were studied by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction techniques that clearly revealed the presence of Cu in the DLC structure. Raman analysis yields that Cu incorporation in DLC enhances the graphite-like sp² bonding. However, the sp² bonding was found to continuously reduce with the increasing C₂H₂ gas pressure, this may be due to reduction of Cu nanocrystal at the higher pressure. FTIR results inferred various bonding states of carbon with carbon, hydrogen and oxygen. In addition, hydrogen content and sp³ and sp² fractions in different Cu-DLC films were also estimated by FTIR spectra and were correlated with stress, electrical, optical and nano-mechanical properties of Cu-DLC films. The effect of indentation load (4–10 mN) on nano-mechanical properties of these films was also explored.     

Electrical and piezoresistive properties of ion beam deposited DLC films

In present study diamond like carbon (DLC) films were deposited by closed drift ion source from the acetylene gas. The electrical and piezoresistive properties of ion beam synthesized DLC films were investigated. Diode-like current–voltage characteristics were observed both for DLC/nSi and DLC/pSi heterostructures. This fact was explained by high density of the irradiation-induced defects at the DLC/Si interface. Ohmic conductivity was observed for DLC/nSi heterostructure and metal/DLC/metal structure at low electric fields. At higher electric fields forward current transport was explained by Schottky emission and Poole–Frenkel emission for the DLC/nSi heterostructures and by Schottky emission and/or space charge limited currents for the DLC/pSi heterostructures. Strong dependence of the diamond like carbon film resistivity on temperature has been observed. Variable range hopping current transport mechanism at low electric field was revealed. Diamond like carbon piezoresistive elements with a gauge factor in 12–19 range were fabricated.     

Structural and optical properties of La-doped BaSnO3 thin films grown by PLD

In this study the structural and optical properties of lanthanum-doped BaSnO₃ powder samples and thin films deposited on fused silica were investigaed using laser ablation. Under an oxygen pressure of 5×10⁻⁴ mbar, phase pure BaSnO₃ films with a lattice constant of 0.417 nm and grain size of 21 nm were prepared at 630 °C. The band gap of BaSnO3 powder sample and thin films was calculated to be 3.36 eV and 3.67 eV, respectively. There was a progressive increase in conductivity for thin films of BaSnO₃ doped with 0~7 at% of La. The highest conductivity, 9 Scm⁻¹, was obtained for 7 at% La-doped BaSnO₃. Carrier concentration, obtained from Burstein-Moss (B-M) shift, nearly matches the measured values except for 3 at% and 10 at% La-doped BaSnO₃ thin films.     

Ge-Sb-Se硫系薄膜制备及光学特性研究

介绍了几种常见的硫系薄膜制备方法, 根据现有实验条件采用热蒸发法和磁控溅射法制备出Ge-Sb-Se三元体系硫系薄膜, 通过台阶仪测试薄膜的厚度和表面粗糙度, 计算出两种制备方法的成膜速率, 并通过X射线光电子能谱测试了两种制备方法所得薄膜与块体靶材组分的差别. 利用Z扫描技术和分光光度计测试了热蒸发法制备所得薄膜的三阶非线性性能和透过光谱, 计算出非线性折射率、非线性吸收系数和薄膜厚度等参数. 结果表明热蒸发法制备Ge-Sb-Se薄膜具有良好的物理结构和光学特性, 在集成光学器件方面很高的应用潜力.     

Study of structural and optical properties of ZnO films grown by pulsed laser deposition

Wurtzite zinc oxides films (ZnO) were deposited on silicon (0 0 1) and corning glass substrates using the pulsed laser deposition technique. The laser fluence, target-substrate distance, substrate temperature of 300 °C were fixed while varying oxygen pressures from 2 to 500 Pa were used. It is observed that the structural properties of ZnO films depend strongly on the oxygen pressure and the substrate nature. The film crystallinity improves with decreasing oxygen pressure. At high oxygen pressure, the films are randomly oriented, whereas, at low oxygen pressures they are well oriented along [0 0 1] axis for Si substrates and along [1 0 3] axis for glass substrates. A honeycomb structure is obtained at low oxygen pressures, whereas microcrystalline structures were obtained at high oxygen pressures. The effect of oxygen pressure on film transparency, band gap E_g and Urbach energies was investigated.     

Correlation of sp and sp fraction of carbon with electrical, optical and nano-mechanical properties of argon-diluted diamond-like carbon films

In the present work the correlation of electrical, optical and nano-mechanical properties of argon-diluted diamond-like carbon (Ar-DLC) thin films with sp³ and sp² fractions of carbon have been explored. These Ar-DLC thin films have been deposited, under varying C₂H₂ gas pressures from 25 to 75 mTorr, by radio frequency-plasma enhanced chemical vapor deposition technique. X-ray photoelectron spectroscopy studies are performed to estimate the sp³ and sp² fractions of carbon by deconvoluting C 1s core level spectra. Various electrical, optical and nano-mechanical parameters such as conductivity, I-V characteristics, optical band gap, stress, hardness, elastic modulus, plastic resistance parameter, elastic recovery and plastic deformation energy have been estimated and then correlated with calculated sp³ and sp² fractions of carbon and sp³/sp² ratios. Observed tremendous electrical, optical and nano-mechanical properties in Ar-DLC films deposited under high base pressure conditions made it a cost effective material for not only hard and protective coating applications but also for electronic and optoelectronic applications.     

金刚石薄膜的红外椭圆偏振光谱研究

采用红外椭圆偏振光谱对微波等离子体化学气相沉积法（MPCVD）和热丝化学气相沉积法（H-FCVD）制备的金刚石薄膜在红外波长范围（2.5—12.5μm）的光学参数进行了测量.建立了不同的光学模型，且在模型中采用Bruggeman有效介质近似方法综合考虑了薄膜表面和界面的椭偏效应.结果表明，MPCVD金刚石膜的椭偏数据在模型引入了厚度为77.5nm的硅表面氧化层、HFCVD金刚石膜引入879nm粗糙层之后能得到很好的拟合.最后对两种模型下金刚石薄膜的折射率和消光系数进行了计算，表明MPCVD金刚石薄膜的红外 关键词： 金刚石薄膜 红外椭圆偏振光谱 光学参数 有效介质近似     

Morphological and optical properties of silicon thin films by PLD

Silicon thin films have been prepared on sapphire substrates by pulsed laser deposition (PLD) technique. The films were deposited in vacuum from a silicon target at a base pressure of 10⁻⁶ mbar in the temperature range from 400 to 800 °C. A Q-switched Nd:YAG laser (1064 nm, 5 ns duration, 10 Hz) at a constant energy density of 2 J × cm⁻² has been used. The influence of the substrate temperature on the structural, morphological and optical properties of the Si thin films was investigated.Spectral ellipsometry and atomic force microscopy (AFM) were used to study the thickness and the surface roughness of the deposited films. Surface roughness values measured by AFM and ellipsometry show the same tendency of increasing roughness with increased deposition temperature.     

激光预处理对光学元件膜层性能的影响

激光预处理是使膜层提高损伤阈值的一种有效手段,现在流行的激光预处理机理模型之一是缺陷消除模型。实验从对元件膜层激光预处理前后各项参数的对比出发,分析了激光预处理对膜层的影响,说明了光学元件膜层激光预处理的过程,是对膜层去除缺陷、固化、洁净的过程。     

激光预处理对光学元件膜层性能的影响

 激光预处理是使膜层提高损伤阈值的一种有效手段，现在流行的激光预处理机理模型之一是缺陷消除模型。实验从对元件膜层激光预处理前后各项参数的对比出发，分析了激光预处理对膜层的影响，说明了光学元件膜层激光预处理的过程，是对膜层去除缺陷、固化、洁净的过程。     

Influence of ion bombardment on growth and properties of PLD created DLC films

A hybrid PLD system with ion bombardment of films was developed. Growing DLC films were modified during the laser deposition (10 J?cm^?2) by argon ions with energy in the range from 40 eV to 210 eV and cathode current of 0.15 A and 0.5 A. The content of sp² “graphitic” and sp³ “diamond” bonds was measured using XPS. Sp³ bonds changed from 60 % to 81 %. We found the highest sp³ content for energy of 40 eV. Hardness (and reduced Young’s modulus) were determined by nanoindentation and reached 49 GPa (277 GPa). Film adhesion was studied using the scratch test and was up to 14 N for titanium substrates. Relations among deposition conditions and measured properties are presented.     

Electrical transport and optical properties of Cd_3As_2 thin films

Cd_3As_2, as a three-dimensional(3D) topological Dirac semimetal, has attracted wide attention due to its unique physical properties originating from the 3D massless Dirac fermions. While many efforts have been devoted to the exploration of novel physical phenomena such as chiral anomaly and phase transitions by using bulk crystals, the development of high-quality and large-scale thin films becomes necessary for practical electronic and optical applications. Here, we report our recent progress in developing single-crystalline thin films with improved quality and their optical devices including Cd_3As_2-based heterojunctions and ultrafast optical switches. We find that a post-annealing process can significantly enhance the crystallinity of Cd_3As_2 in both intrinsic and Zn-doped thin films. With excellent characteristics of high mobility and linear band dispersion, Cd_3As_2 exhibits a good optical response in the visible-to-mid-infrared range due to an advantageous optical absorption, which is reminiscent of 3D graphene. It also behaves as an excellent saturable absorber in the mid-infrared regime. Through the delicate doping process in this material system, it may further open up the long-sought parameter space crucial for the development of compact and high-performance mid-infrared ultrafast sources.     

ZrO2薄膜微观结构和光学性能的研究

无论是在300℃或室温下,用PVD方法淀积的ZrO_2薄膜,达到一定厚度后都出现晶相非均匀性,在基底侧为四方相,空气侧为单斜相.本文给出了ZrO_2薄膜中四方相存在的原因,并用晶体生长过程中的择优生长特性讨论了薄膜柱状体结构的成因,从而解释了薄膜的折射率非均匀性.     

Fabrication and optical properties of SnS thin films by SILAR method

Although the fabrication of tin disulfide thin films by SILAR method is quiet common, there is, however, no report is available on the growth of SnS thin film using above technique. In the present work, SnS films of 0.20 μm thickness were grown on glass and ITO substrates by SILAR method using SnSO₄ and Na₂S solution. The as-grown films were smooth and strongly adherent to the substrate. XRD confirmed the deposition of SnS thin films. Scanning electron micrograph revealed almost equal distribution of the particle size well covered on the surface of the substrate. EDAX showed that as-grown SnS films were slightly rich in tin component while UV-vis transmission spectra exhibited high absorption in the visible region. The intense and sharp emission peaks at 680 and 825 nm (near band edge emission) dominated the photoluminescence spectra.     

纳米ZnO和ZnO-SiO2复合薄膜的光学性质研究

通过溶胶凝胶(sol-gel)法分别在玻璃衬底上制备了ZnO纳米薄膜和ZnO-SiO2纳米复合薄膜,并利用紫外.可见光分光光度计对薄膜的光学性能进行了分析.可见光一紫外透射谱显示,随着Zn0溶胶浓度从0.7 mol/L降低到0.006 mol/L,制备的ZnO薄膜从只出现一个380 nm(对应的光学禁带宽度为3.27 eV)左右的吸收边到在380和320nm(对应的光学禁带宽度为3.76 ev)左右各出现一个吸收边,并且随着ZnO溶胶浓度的降低,在380-320 nm波段内的透过率明显提高.而ZnO-SiO2复合薄膜只在310 nm左右出现一个吸收边.SiOO2的包覆宽化了ZnO的禁带宽度,包覆后的禁带宽度可达到3.87 ev.     

Synthesis of DLC films by PLD from liquid target and dependence of film properties on the synthesis conditions

DLC (Diamond-like carbon films) were prepared by pulsed laser ablation of a liquid target at substrate temperatures from 18 to 600°C using 248 nm KrF excimer laser. The sp³ hybridization state carbon formation was additionally promoted by gaseous H₂O₂ flow through the reaction chamber and substrate excitation by the same laser beam. Deposited DLC films were characterised by Raman scattering spectroscopy and atomic force microscopy (AFM). Comparative AFM and Raman study shows that the increase in the content of sp³ type bonding in DLC is in correlation with the increase of the surface roughness of the samples prepared.