Coherent thermal radiation in thin films and its application in the emissivity design of multilayer films

The infrared transmission spectra of a 0.54-μm-thick Ge film and a 20-μm-thick Si film were experimentally measured. As the incident radiation was in the wavelength range from 1.5μm to 10μm, the Ge film demonstrated a strongly spectral coherence. However, thermal radiation of the Ge film was found to be spatially incoherent due to its extreme thinness. The Si film exhibited significantly spectral and spatial coherence. The results confirmed that thermal radiation of a monolayer film could be coherent spectrally and spatially if the film thickness was comparable with the wavelength. The optical characteristic matrix method was applied to calculate the transmission spectra of the Si and Ge film, and the results agreed well with the measurements. This method was further used to analyze two multilayer films composed of five low emissive layers. Their emissivities were found to be highly emissive at a certain zenith angle, and the emissive peak could be controlled by careful selection of film thickness.     

GaAs薄膜的瞬态光致折射率变化研究

利用飞秒瞬态反射谱和透射谱，研究了ＧａＡｓ薄膜的瞬态光致折射率变化，观察到光致折射率的一个超快弛豫过程和一定激发浓度下的瞬态光致吸收增加现象，用受激载流子引起的带填充和能隙收缩解释了这些现象。     

A novel approach to design microwave medium of negative refractive index and simulation verification

In this paper, a novel approach is presented to synthesize microwave medium of negative refractive index by incorporating metallic wire array with negative effective permittivity into the host media such as ferrimagnet-YIG （yttrium iron garnet） applied by external magnetic field whose permeability is negarive. We have designed the composite medium having negative refractive index in C/X band frequencies, analyzed and simulated its electromagnetic （EM） properties by use of EM EDA package based on time-domain finite integration method. The simulation results show that： ① the effective permittivity of the designed metallic wire array is negative in the frequency range from 7.02 GHz to 9.80 GHz; ② the permeability of YIG substrate immersed into an external magnetic field is negative in the frequency range from 5.22 GHz to 8.14 GHz; ③ EM wave can pass through the composite medium synthesized by the above designed metallic wire array and YIG substrate, and ④ the negative refraction behavior occurs on the interface between the composite medium and the normal material with positive refractive index in 7.51-8.13 GHz frequency range, in which the effective permitUvity of the metallic wire array and the permeability of YIG substrate are negative simultaneously. The full wave simulation has demonstrated that the effective refractive index of the designed composite medium is indeed negative and ascertained that the proposed approach to design microwave medium with negative refractive index is viable.     

负偏压对六方氮化硼薄膜沉积特性的影响

利用射频磁控溅射法在n型Si(100)衬底上沉积六方氮化硼薄膜(h-BN),采用AFM、Raman、XPS、FTIR等技术研究负偏压对所沉积薄膜生长模式、结构、表面粗糙度、薄膜取向、相变等特性的影响。结果表明,当负偏压为0V时,沉积所得h-BN薄膜表面粗糙度较低、结晶性良好、c轴垂直于衬底且以层状模式生长;随着负偏压的增加,薄膜由层状模式生长转变为岛状模式生长,表面粗糙度增加,且h-BN经亚稳相E-BN和wBN向c-BN转变,使得BN薄膜相系统更加混乱,不利于高质量层状h-BN薄膜的获取。     

ZrW2O8薄膜的物相转变与负热膨胀系数

以高纯ZrO2和WO3复合氧化物为靶材,采用射频磁控溅射方法在石英基片上制备ZrW2O8薄膜.对不同热处理温度后的薄膜进行XRD分析,结果表明,在650 ℃下薄膜为无定形,ZrW2O8晶化起始温度为650 ℃,当热处理温度高于1 100 ℃时,薄膜主要由ZrO2相组成.进一步采用高温XRD分析薄膜物相,发现在720 ℃时,能获得较纯的ZrW2O8薄膜.根据ZrW2O8晶面(2 1 1)间距随温度变化的结果,计算所制备的薄膜态ZrW2O8的热膨胀系数为-2.54×10-5/℃.SEM分析结果显示在ZrW2O8相所存在的温度范围内,薄膜非常致密而无明显孔洞.     

压强和温度对薄膜折射率的影响模型

基于膜分子和气相分子在沉积时竞争的观点,得到压强和温度对薄膜折射率影响的理论模型.模型的研究表明,薄膜折射率随真空压强的增加而降低;并随沉积温度的增加而增加.在不同真空压强和不同沉积温度下制备了氧化锆薄膜,计算了样品的折射率,结果显示的规律和理论模型的规律基本一致.     

Thermal radiation characteristics of plane-parallel SiC wafer

The spectral and directional absorptivity of plane-parallel SiC wafer is investigated in the IR region. The result demonstrates that interference takes place for thermal radiation emitted by plane-parallel SiC layers of the thickness from several tens to 100 microns. Owing to particular optical property of SiC, the spectral absorptivity of 10-micron radiant wave is 0.98, close to I, the absorptivity of black body. Nevertheless, the absorptivity approaches 0 in the range from 10.5 to 12.4 microns wavelength. Our calculation also shows that total hemispherical emissivity relates to wafer‘s temperature. It is between 300 and 500K where higher total hemispherical emissivity exists.     

电磁波在芯层为负折射率媒质的介质波导中的传播

分析了电磁波在正负折射率媒质界面、两种负折射率媒质界面处的传播特性,并对负折射率媒质为芯层(波导层)的介质波导的传播规律进行了探讨.其结论对于丰富波导理论和进一步研究电磁波在负折射率媒质中的传播特性及微波毫米波相关器件的设计有着重要的意义.     

管式PECVD工艺对氮化硅薄膜折射率的影响

折射率是反映薄膜成分以及致密性的重要指标, 是检验薄膜制备质量的重要参数,其变化直接影响太阳能电池的转化效率。本文研究了不同射频功率、腔体压强、衬底温度以及硅烷和氨气配比等沉积条件对在太阳能电池上沉积的氮化硅薄膜折射率的影响,分析了氮化硅薄膜折射率随各沉积条件变化的原因。     

液体折射率的干涉法测量

液体折射率的测量在工农业生产中非常重要,利用牛顿环干涉原理测量液体的折射率的方法,能够方便、准确地测量出液体的折射率,测量结果准确,测量过程简单。     

均质非平衡态分子动力学模拟铜薄膜的热导率

为研究微电子器件中薄膜的“超常”传热行为，基于等温线性响应理论（LRT）和嵌入原子法（EAM）势函数，采用均质非平衡态分子动力学方法，对铜薄膜的热导率进行了计算机数值模拟，给出了铜薄膜热导率与薄膜厚度及温度之间的关系，模拟结果符合Flik关于微尺度薄膜导热的判据并与其他文献的实验数据基本一致，表明该方法和结果可以利用于微电子器件中的微尺度传热及热应力问题的分析。     

测定薄透镜曲率半径和折射率的简单方法

介绍了薄透镜焦距测定中观察到的一种反射成像现象,指出利用薄透镜正反两次反射成像可较好地测定其折射率和前后表面的曲率半径。     

Analysis on mechanism of thin film lubrication

It is an important concern to explore the properties and principles of lubrication at nano or molecular scale. For a long time, measurement apparatus for film thickness of thin film lubrication （TFL） at nano scale have been devised on the basis of superthin interferometry technique. Many experiments were carried out to study the lubrication principles of TFL by taking advantages of aforementioned techniques, in an attempt to unveil the mechanism of TFL. Comprehensive experiments were conducted to explore the distinctive characteristics of TFL. Results show that TFL is a distinctive lubrication state other than any known lubrication ones, and serves as a bridge between elastohydrodynamic lubrication （EHL） and boundary lubrication （BL）. Two main influence factors of TFL are the solid surface effects and the molecular properties of the lubricant, whose combination effects result in alignment of liquid molecules near the solid surfaces and subsequently lubrication with ordered film emerged. Results of theoretical analysis considering microstructure are consistent with experimental outcomes, thus validating the proposed mechanism.     

用等厚干涉测液体折射率

采用劈尖实验装置在不改变劈尖膜条件下,同时测得空气膜和液体膜的干涉条纹宽度,并进一步计算出实验结果,从而得到一种方便求出液体折射率的新方法.     

负偏压对反应磁控溅射AlN薄膜的影响

利用反应磁控溅射制备AlN薄膜,研究了基底负偏压对薄膜结构及其性能的影响.XRD和SEM结果表明:用此方法获得的AlN薄膜呈晶态,负偏压对AlN择优取向产生一定的影响,随着偏压的增大,薄膜表面晶粒尺寸有长大趋势.根据透射谱测试和包络线计算结果可知,薄膜在可见光和红外区域透射率高,随着偏压的增大,薄膜的折射率也随之增大.     

Molecular dynamics study on thermal conductivity of nanoscale thin films

A simple and effective model of heat conduction across thin films is set up and molecular dynamics simulations are implemented to explore the thermal conductivity of nanoscale thin dielectric films in the direction perpendicular to the film plane. Solid argon is selected as the model system due to its reliable experimental data and potential function. Size effects of the thermal conductivity across thin films are found by computer simulations: in a film thickness range of 2–10 nm, the conductivity values are remarkably lower than the corresponding bulk experimental data and increase as the thickness increases. The consistency between the approximate solution of the phonon Boltzmann transport equation and the simulation results ascribes the thermal conductivity size effect to the phonon scattering at film boundaries.     

超薄氩膜热传导的分子动力学模拟

采用基于经典理论的平衡态分子动力学(EMD))方法，在无量子化修正的条件下，计算了固态氩(Ar)在低于其Debye温度(92K)下的导热系数．温度在20K以上时，模拟结果和实验值吻合较好，说明固态Ar的量子化效应对其热传导性能影响不大，温度低于20K时，由于模拟区域对长波声子的裁剪作用使得模拟结果比实验值低．在此基础上，使用经典分子动力学基于三向、两向周期性边界条件的各向异性非平衡态薄膜模型，模拟了超薄Ar膜在40K的导热系数，2种模型给出了具有相同变化趋势的薄膜热传导特性曲线，即：随着膜厚的增加，导热系数增大，且模拟结果同模拟区域横截面大小无关．在相同条件下，2种模型得到的氩膜导热系数相差10％左右．     

钯催化三氧化钨薄膜对氢气的感应特性

以对氢气易于反应的钯为催化材料、钯的沉积厚度和热处理条件为变量,研究三氧化钨薄膜的物理化学性能及气体反应特性。结果表明,三氧化钨在500 ℃以上时呈现四方晶体的多晶态,钯沉积对三氧化钨的晶体结构没有影响,但是随着钯的添加抑制了三氧化钨的晶粒生长。500 ℃以上热处理时钯在薄膜表面呈现小球状,600 ℃以上热处理时钯粒子在薄膜表面凝结或扩散到材料内部。沉积钯 2 nm的薄膜在工作温度250 ℃时反应灵敏度和恢复特性对氢气的检测特性最好。     

空气折射率测量实验的改进

普通的迈克尔逊干涉仪测量空气折射率遇到的主要问题是由于光程差太大,使得干涉条纹很密无法计数。该文介绍的用测微目镜将干涉条纹放大,再进行测量的方法很好地解决了这个问题。     

氮化铝(AIN)薄膜的光学特性研究

研究了宽禁带Ⅲ－Ｖ族化合物半导体氮化铝（ＡＩＮ）薄膜的折射率及其热光特性,采用棱镜──薄膜耦合装置和自动温控光波导测试仪,测出不同温度下氮化铝薄膜的波导特性,利用迭代法可得到ＡＩＮ的折射率与温度变化的关系,并首次测得了ＡＩＮ薄膜的热光特性。