a-C:F薄膜的热稳定性与光学带隙的关联

以CF4和C6H6的混合气体作为气源,在微波电子回旋共振化学气相沉积(ECRCVD)装置中制备了氟化非晶碳薄膜(aC:F),并在N2气氛中作了退火处理以考察其热稳定性.通过傅里叶变换红外吸收谱和紫外可见光谱获得了薄膜中CC双键的相对含量和光学带隙,发现膜中CC键含量与光学带隙之间存在着密切的关联,在高微波功率下沉积的氟化非晶碳膜具有低的光学带隙和较好的热稳定性. 关键词： 氟化非晶碳膜 光学带隙 退火温度 热稳定性     

电子回旋共振等离子体增强化学气相沉积a-CFx薄膜的化学键结构

使用CHF₃和C₆H₆混合气体做气源,在一个电子回旋共振等离子体增强化学气相沉积装置中制备了氟化非晶碳(a-CF_x)薄膜.利用发射光谱研究了等离子体中形成的各种碳氟、碳氢基团随放电宏观参量的变化规律,对薄膜做了傅里叶变换红外光谱和X射线光电子能谱分析,证实等离子体中的CF₂,CF和CH基团是控制薄膜生长、碳/氟成分比和化学键结构的主要前驱物 关键词： 氟化非晶碳薄膜 电子回旋共振等离子体     

氟化非晶碳薄膜的光学带隙分析

研究了CHF3C6H6沉积的氟化非晶碳(αC∶F)薄膜的光学带隙.发现αC∶F薄膜光学带隙的大小取决于薄膜中C—F,CC的相对含量.这是由于CC形成的窄带隙π键和C—F形成的宽带隙σ键含量的相对变化,改变了带边态密度分布的结果.在微波功率为140—700W、沉积气压为01—10Pa、源气体CHF3∶C6H6流量比为1∶1—10∶1条件下沉积的αC∶F薄膜,光学带隙在176—398eV之间 关键词： 氟化非晶碳(αC∶F)薄膜 光学带隙 键结构     

微波输入功率引起a-C∶F薄膜交联结构的增强

使用C2H2和CHF3的混合气体,在改变微波功率的条件下,利用微波电子回旋共振等离子体增强化学气相沉积方法制备了氟化非晶碳薄膜(aC∶F).薄膜的傅里叶变换红外光谱分析结果表明:薄膜中的CC与C—F键含量的比值随功率的增加而相应地增大;借助于紫外可见光谱分析发现,薄膜的光学带隙随功率的增大而减小.由此推断微波输入功率的提高有助于增强薄膜的交联结构.aC∶F薄膜的交流电导与x射线光电子能谱进一步证实了这种增强效应 关键词： 氟化非晶碳薄膜 傅里叶变换红外光谱 x射线光电子能谱     

微波电子回旋共振等离子体增强化学气相沉积法沉积氟化非晶碳薄膜的研究

使用三氟甲烷和苯的混合气体,利用微波电子回旋共振等离子体增强化学气相沉积法制备了F/C比在0.11—0.62之间的α-C∶F薄膜.研究了微波功率对薄膜沉积和结构的影响,发现微波功率的升高提高了薄膜的沉积速率,降低了薄膜的F/C比,也降低了薄膜中CF和CF₃基团的密度,而使CF₂基团的密度保持不变.在高微波功率下可以获得主要由CF₂基团和C=C结构组成的α-C∶F薄膜.薄膜的介电频率关系(1×10³—1×10⁶Hz)和损耗频率关系(1×10²—1×10⁵Hz)均呈指数规律减小,是缺陷中心间简单隧穿引起的跳跃导电所致.α-C∶F薄膜的介电极化主要来源于电子极化 关键词： 氟化非晶碳薄膜 ECR等离子体沉积 键结构 介电性质     

源气体对沉积的a-C∶F∶H薄膜结构的影响

采用微波电子回旋共振等离子体化学气相沉积(MWPECRCVD)方法,使用不同的源气体(CHF3CH4,CHF3C2H2,CHF3C6H6)体系制备了aC∶F∶H薄膜.由于CH4,C2H2,C6H6气体在等离子体中的分解反应不同导致了薄膜的沉积速率和结构上的差异.红外吸收谱的结果表明,用C6H6CHF3作为源气体沉积的薄膜中几乎不含H,而用C2H2CHF3所沉积的薄膜中的含氟量最高,其相应的CF振动峰位向高频方向偏移.薄膜的真空退火结果表明,aC∶F∶H薄膜的热稳定性除了取决于薄膜的CC键浓度外,还与CC键 关键词： 氟化非晶碳膜 电子回旋共振化学气相沉积 红外吸收光谱     

电子回旋共振等离子体增强化学气相沉积a-CF_x薄膜的化学键结构

使用CHF3 和C6H6混合气体做气源 ,在一个电子回旋共振等离子体增强化学气相沉积装置中制备了氟化非晶碳 (a CFx)薄膜 .利用发射光谱研究了等离子体中形成的各种碳 氟、碳 氢基团随放电宏观参量的变化规律 ,对薄膜做了傅里叶变换红外光谱和X射线光电子能谱分析 ,证实等离子体中的CF2 ,CF和CH基团是控制薄膜生长、碳 /氟成分比和化学键结构的主要前驱物     

含氮氟化类金刚石(FN-DLC)薄膜的研究：(Ⅱ)射频功率对薄膜光学带隙的影响

以CF₄,CH₄和N₂为源气体，采用射频等离子体增强化学气相沉积法，在不同射频功率下制备了含氮氟化类金刚石薄膜样品.原子力显微形貌显示，低功率下沉积样品表面致密均匀.拉曼及傅里叶变换红外光谱分析显示，随着射频功率的改变，薄膜的结构和组分也随之变化.紫外-可见光透射光谱证明薄膜具有紫外强吸收特性，通过计算得到其光学带隙在1.89—2.29 eV之间.结果表明，射频功率增加，薄膜内sp²C含量增加，或者说C=C交联相对浓度增加、F的相对浓度降低，导致薄膜内π-π^*带边态密度增大，光学带隙减小. 关键词： 含氮氟化类金刚石薄膜 射频功率 光学带隙     

ECR-CVD法制备的a-C:F:H薄膜在N2气氛中的热退火研究

改变CHF3CH4源气体流量比,使用微波电子回旋共振化学气相沉积方法(ECRCVD)制备了具有不同C—F键结构的aC:F:H薄膜,着重研究了退火对其结构的影响.结果显示薄膜的厚度及其光学带隙E04随退火温度的上升均呈现了不同程度的下降.借助于红外吸收光谱和所提出的热解模型解释了产生这种关系的结构上的根源. 关键词： 电子回旋共振化学气相沉积 红外吸收光谱 热退火 光学带隙     

HW-MWECR-CVD法制备氢化微晶硅薄膜及其微结构研究

用热丝辅助微波电子回旋共振化学气相沉积方法制备出高晶化体积分数的氢化微晶硅(μc-Si:H)薄膜.拉曼散射和X射线衍射技术对样品的微观结构测量分析表明，当反应气体中SiH₄浓度在3.6%—50%之间大范围变化时，μc-Si:H薄膜均具有高的晶化体积分数.进一步的分析表明，在SiH₄浓度较大时制备的薄膜，其结构以非晶-微晶的过渡相为主.薄膜易于晶化或生长为过渡相的主要原因是微波电子回旋共振使SiH₄气体高度分解，等离子体高度电离. 关键词： 微波电子回旋共振化学气相沉积 氢化微晶硅薄膜 拉曼散射 X射线衍射     

退火对含氮氟非晶碳膜结构及光学带隙的影响

采用射频等离子体增强化学气相沉积法,在不同条件下制备了含氮氟非晶碳膜,着重考察了退火温度对膜结构和光学带隙的影响. 研究发现：在350℃时,膜仍很稳定,当退火温度达到400℃时,其内各化学键的相对含量发生很大的改变. 膜的光学带隙随着退火温度的升高而增大,红外和拉曼光谱分析显示其原因是：退火使得膜内F的相对浓度降低,sp²相对含量升高,导致σ-σ^*带边态密度降低. 关键词： 含氮氟非晶碳膜 退火 光学带隙     

不同CHF3/CH4流量比下沉积a-C∶F∶H薄膜键结构的红外分析

通过微波电子回旋共振等离子体化学气相沉积方法使用CH₄/CHF₃源气体制备a-C∶F∶H薄膜.红外结果表明,a-C∶F∶H薄膜随着流量比R=[CHF₃]/[CHF₃]+[CH₄])的变化存在结构上的演变,R<64%时,薄膜主要是以类金刚石(DLC)特征的结构为主;当R>64%时,薄膜表现为一个类聚四氟乙烯(PTFE)的结构,结构单体主要为CF₂.同时这种结构上的变化影响着薄膜 关键词： a-C∶F∶H薄膜 傅里叶变换红外光谱 紫外可见光谱     

反应磁控溅射法制备的氟化类金刚石薄膜的XPS结构研究

采用射频反应磁控溅射法用高纯石墨作靶、三氟甲烷(CHF₃)和氩气(Ar)作源气体制 备了氟化类金刚石（FDLC）薄膜，通过XPS光谱结合拉曼光谱、红外透射光谱和紫外 可见光光谱研究了源气体流量比等工艺条件对薄膜中键结构、sp2/sp3杂化比以及光学带隙等性能的影响.结果表明在低功率(60W)、高气压(2.0Pa)和适当的流量比(Ar/CHF₃=2∶ 1)下利用射频反应磁控溅射法可制备出氟含量高且具有较宽光学带隙和超低介电常数的FDLC薄膜. 关键词： 反应磁控溅射 氟化类金刚石薄膜 红外透射光谱 XPS光谱     

Synthesis and optical properties of basic fuchsin dye-doped PMMA polymeric films for laser applications: wide scale absorption band

Basic fuchsin dye-doped poly(methyl methacrylate) polymeric films were sensitized with various dye concentrations ranging from 0.0833 to 1.667 wt% of basic fuchsin. Their structure, linear absorption, and optical limiting properties were examined. The films were prepared using a simple and fast casting technique dissolved in chloroform for both the dye and the polymer. Structural characterizations were achieved by XRD, and the films showed an amorphous hump supporting the noncrystalline structure of studied polymeric composites. Spectrophotometer measurements were used to estimate the spectral absorption measurements of the films such as transmittance, absorbance with the calculations of absorption index (k), and optical energy band gap (E _g ) in the wavelength region from 190 to 2500 nm. Results show that the optical constants change with increasing the dye doping concentrations. It has been found that optical energy gap (E _g ) appearing that, both direct and indirect optical transitions are conceivable for these films. Optical limiting properties of the films with various dye concentrations were studied using a continuous wave He–Ne laser operating at 632.8 nm. The results appeared that the sample has an obvious optical limiting effect. The designed BF/PMMA composites can be applicable in wide-scale applications.     

UV photoprotection of Osthol

In the present paper, Osthol (molecular formula: C₁₅H₁₆O₃; molecular mass: 244) was obtained from the plant Prangos pabularia by column chromatography technique. This compound was simultaneously exposed to short- (254?nm) and long-wavelength (365?nm) ultraviolet (UV) radiations for different time periods. These irradiated samples were characterized by UV–Visible spectroscopy. No significant variation in optical absorbance/transmittance in broad (200–365?nm) spectrum is observed with increasing dose. The effect of temperature on optical absorption is also insignificant. Effect of UV radiation and temperature on optical band gap (E_g), Urbac energy, or disorder energy (E_u) was also analyzed. A small impact on these optical parameters (E_g and E_u) was observed. This molecule seems very stable (at molecular level) under the influence of UV radiations and temperature. These observed properties shown by this compound projects it as a potential UV protection material.     

Specific features of the optical and electrical properties of polycrystalline CdTe films grown by the thermal evaporation method

The results of studying the physical properties of thin CdTe films obtained by the thermal evaporation method have been presented. The optical constants and the band gap of the films under study have been determined (E _g = 1.46 eV). It has been established based on the investigation of optical properties and the Raman spectrum of the films that they possess high structural quality. The activation energy of the electrical conductivity of CdTe films has been determined: E _a = 0.039 eV. The measured spectral dependences of the impedance of CdTe thin films are characteristic of the inhomogeneous medium with two time constants: τ_gb = R _gb C _gb = 1/ω_gb = 1.62 × 10^?3 s and τ_g = R _g C _g = 1/ω_g = 9.1 × 10^?7 s for grain boundaries and grains, respectively.     

BaO半导体薄膜在外加垂直表面电场作用下的近紫外光吸收增强现象研究

通过对真空蒸发沉积制备的BaO半导体薄膜在外加垂直表面电场作用下光吸收特性的测试, 实验上观察到BaO薄膜在近紫外波段的光吸收随电场强度的增加而明显增强.理论分析表明, BaO半导体薄膜在外加垂直表面电场作用下发生能带倾斜,价带电子隧穿带间位垒而在带隙 中出现的概率增加,近紫外波段光吸收增强是光子协助隧道穿越的结果.不同能量光子激发 下电场作用引起的BaO薄膜光吸收增强现象是夫兰茨-凯尔迪什(Franz-Keldysh)效应和斯塔 克(Stark)效应在金属氧化物半导体材料上的体现. 关键词： 金属氧化物半导体薄膜 光子协助隧道效应 电致吸收 夫兰茨-凯尔迪什效应     

Structural and optoelectronic properties of amorphous GaN thin films

Amorphous gallium nitride (a-GaN) thin films were deposited on glass substrate by electron beam evaporation technique at room temperature and high vacuum using N ₂ as carrier gas. The structural properties of the films was studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). It was clear from XRD spectra and SEM study that the GaN thin films were amorphous. The absorbance, transmittance and reflectance spectra of these films were measured in the wavelength range of 300–2200 nm. The absorption coefficient spectral analysis in the sharp absorption region revealed a direct band gap of E _g = 3:1 eV. The data analysis allowed the determination of the dispersive optical parameters by calculating the refractive index. The oscillator energy E ₀ and the dispersion energy E _d, which is a measure of the average strength of inter-band optical transition or the oscillator strength, were determined. Electrical conductivity of a-GaN was measured in a different range of temperatures. Then, activation energy of a-GaN thin films was calculated which equalled E _a = 0:434 eV.     

Thermally and optically induced effects on sub-band gap absorption in nanocrystalline CdSe (nc-CdSe) thin films

Nanocrystalline cadmium selenide (nc-CdSe) thin films have been prepared by thermal evaporation using the inert gas condensation (IGC) technique. Transmission electron microscopy (TEM) studies show that the CdSe nanocrystals (NCs) are spherical in shape. Constant photocurrent method (CPM) is used to determine the value of absorption coefficient in low absorption region of as-deposited, annealed and light soaked nc-CdSe thin films. Values of optical band gap (E_g) have been determined by using Tauc's relation for as-deposited, annealed and light soaked nc-CdSe thin films from the α values evaluated from reflection and transmission measurements. We have used a derivative procedure to sub-gap absorption spectra in order to get information on the energetic distribution of the occupied density of states below Fermi level. Constants such as optical gap E_g, Urbach edge E_u have been obtained from CPM spectra in as-deposited, annealed and light soaked nc-CdSe thin films. Concentration of defect states has also been calculated in as-deposited, annealed and light soaked nc-CdSe thin films.     

PHOTO- AND ELECTRO-LUMINESCENCE FROM HYDROGENATED AMORPHOUS SILICON CARBIDE FILMS PREPARED BY USING ORGANIC CARBON SOURCE

Hydrogenated amorphous silicon carbide (a-SiC:H) films were grown by using an organic source, xylene (C₈H₁₀), instead of methane (CH₄) in a conventional plasma enhanced chemical vapor deposition system. The optical band gap of these samples was increased gradually by changing the gas ratio of C₈H₁₀ to SiH₄. The film with high optical band gap was soft and polymer-like and intense photoluminescence were obtained. Room temperature electro-luminescence was also achieved with peak energy at 2.05 eV (600 nm) for the a-SiC:H film with optical band gap of 3.2 eV.