Characterization of native and adsorbed thin films on silicon detector surfaces: static and kinetic applications

The photoelectric response of a windowless reflective silicon photodetector for obliquely incident polarized monochromatic light is used to characterize the native passivation dielectric thin film at the detector surface. In the presence of adsorption, the generated photoelectric signal becomes a function of the thickness and refractive index of the adsorbed layer. Higher sensitivity is achieved with s-polarized light and at incidence angles> 60 °. Furthermore, the passivation layer can be optimized for a specific adsorption experiment. A sensor of this kind is used to study the adsorption kinetics of H₂O at the detector surface and the results are interpreted by Bruggeman's effective medium theory. If a second detector is introduced to intercept the light reflected by the first detector, and the polarization of the incident light is modulated, analysis of output signals of this two-detector system determines the responsivity, absolute reflectances, and ellipsometric parameters of the first detector surface.     

Thermophysical Properties of the Refrigerant Mixtures R410A and R407C from Dynamic Light Scattering (DLS)

Dynamic light scattering (DLS) has been used for the measurement of several thermophysical properties of the refrigerant mixtures R410A and R407C. Thermal diffusivity and sound speed have been obtained by light scattering from bulk fluids for both the liquid and vapor phases under saturation conditions over a temperature range from about 290 K up to the liquid-vapor critical point. By applying the method of DLS to a liquid-vapor interface, also called surface light scattering (SLS), the saturated liquid kinematic viscosity and surface tension can be determined simultaneously. These properties have been measured for R410A and R407C from about 240 to 330 K and 240 to 350 K, respectively. The results are discussed in detail in comparison with literature data and with a simple prediction method based on the mass-weighted properties of the pure components expressed as functions of the reduced temperature.     

Scatter-ratio test for lens surface-quality measurement

The surface quality of an optical lens can be quantitatively measured using a scatter ratio test. A collimated light beam is focused by the test lens upon an opaque spot. A detector behind the spot measures light scattered past the spot. The spot is then displaced to the side so that total energy out of the lens is measured by the detector. The scatter ratio is the ratio of the two detector outputs. The test is shown to be reproducible and insensitive to operator effects. It is shown to be an effective process control tool for detecting changes in surface finish. The relationship between stylus measurements of lens surface roughness and the scatter ratios is shown.     

Instrumentation to measure the backscattering coefficient b(b) for arbitrary phase functions

A single detector instrument concept that collects scattered light over the full range of backscattering angles is described. Its light collection aperture is designed so as to introduce a sin θ factor into the collection probability. Hence, the instrument is exactly a b(b) meter; it directly measures b(b), not a proxy for it. For an infinitesimal aperture to the detector, the instrument would give b(b) exactly; for a finite aperture (e.g., 1.26 cm(2)), it would typically give b(b) to an accuracy of a few tenths of 1%. The instrumentation itself is as simple as that of the well-known fixed-angle meters-it projects a beam of light into the medium and collects backscattered light with a single detector; the differences are the position of the detector and the shape/orientation of the entrance aperture to the detector.     

Development of a detector for liquid chromatography based on aerosol chemiluminescence on porous alumina

This paper describes a novel aerosol chemiluminescence-based detector, which can be coupled to liquid chromatography for the determination of the chemicals with weak optical absorbance in the UV-visible region. This aerosol chemiluminescence (CL)-based detector, in which HPLC effluent is converted to aerosol and then generated CL emission on the surface of porous alumina, is composed of three main processes: nebulization of HPLC effluent, CL emission on surface of porous alumina material, and optical detection. To demonstrate the utility of the aerosol chemiluminescence detector, some compounds such saccharides, poly(ethylene glycol)s, amino acids, and steroid pharmaceuticals are determined by the present aerosol chemiluminescence detection method. Compared with an evaporative light scattering detector, the proposed detector shows the following features: (a) extensive CL emissions on porous alumina by many compounds tested, which leads to the potential application for the determination of volatile and nonvolatile chemicals with or without UV-visible absorbance; (b) a CL mechanism based on the catalytic oxidation of analytes, not on the light scattering, which suggests the present detector be free from the interference of the inorganic and nonvolatile mobile-phase modifiers. The CL characteristics and effect of different parameters, such as temperature and nebulizer gas flow rate, were also discussed in this paper. Furthermore, this aerosol chemiluminescence-based detector was successfully applied to the determination of raffinose, glucose, sucrose, maltose, and alpha-lactose.     

Accuracy of position detection using a position-sensitive detector

Position-sensitive detectors (PSD) provide four current outputs that are proportional to the two-dimensional center of mass of a light spot impinging on the face of the detector. This characteristic permits the PSD to be used for sensing the position of a light source. The application motivating the work reported here involved the tracking of a light source located on a surface with approximate dimensions 122 cm wide by 91 cm high located approximately 2 m from the detector. The diameter of the light source was a few millimeters. The work described here demonstrates the feasibility of using a PSD to track the position of a light source with accuracy better than 1 mm from this distance     

Light detector development for CRESST II

CRESST-II detector modules rely on the ability to actively discriminate electron recoils from nuclear recoils via simultaneous measurement of phonons and scintillation light. The scintillation light produced in each target crystal is detected via an associated calorimeter consisting of a thin silicon wafer read out by a tungsten phase transition thermometer deposited on its surface. About 1% of the energy deposited in CaWO₄ is detected as scintillation light; therefore, the sensitivity of the light detector is crucial for the discrimination of electron recoils from nuclear recoils at energies relevant for WIMP searches. We report the detector performance obtained using a thermometer geometry characterized by phonon collectors and a thin film thermal coupling to the heat sink (Fig. 1). This concept allows a high sensitivity by decoupling the area required for the collection of non-thermal phonons and the heat capacity of the sensor. With a 30×30×0.45 mm³ light detector, energy thresholds below 5 keV referred to energy deposition in CaWO₄ have been obtained. Results achieved will be presented and an overview on further possibilities of development will be given.     

Saturated Liquid Viscosity and Surface Tension of Alternative Refrigerants

Light scattering by thermally excited capillary waves on liquid surfaces or interfaces can be used for the investigation of viscoelastic properties of fluids. In this work, we carried out the simultaneous determination of the surface tension and the liquid kinematic viscosity of some alternative refrigerants by surface light scattering (SLS) on a gas–liquid interface. The experiments are based on a heterodyne detection scheme and signal analysis by photon correlation spectroscopy (PCS). R23 (trifluoromethane), R32 (difluoromethane), R125 (pentafluoroethane), R143a (1,1,1-trifluoroethane), R134a (1,1,1,2-tetrafluoroethane), R152a (1,1-difluoroethane), and R123 (2,2-dichloro-1,1,1-trifluoroethane) were investigated under saturation conditions over a wide temperature range, from 233 K up to the critical point. It is estimated that the uncertainty of the present surface tension data for the whole temperature range is less than ±0.2 mN·m^–1. For temperatures up to about 0.95T _c, the kinematic viscosity of the liquid phase could be obtained with an absolute accuracy of better than 2%. For the highest temperatures studied in this work, measurements for the kinematic viscosity exhibit a maximum uncertainty of about ±4%. Viscosity and surface tension data are represented by a polynomial function of temperature and by a van der Waals-type surface tension equation, respectively. The results are discussed in detail with comparison to literature data.     

光子在闪烁晶体中传输的蒙特卡罗模拟

为了找到构筑闪烁晶体探测器的优化方法，使用蒙特卡罗方法对闪烁晶体BGO（Bi4Ge3O12，锗酸铋）的光收集效率进行了模拟研究。模拟结果表明：入射面为粗糙面，其余为抛光面，同时外层包装上高反射率的材料，可得到最大的光输出（约59．1％的光子被收集）；耦合剂的折射率的得到高的光输出也起着非常重要的作用。     

Response mechanisms of thermionic detectors with enhanced nitrogen selectivity.

The response mechanisms of a thermionic detector with enhanced nitrogen selectivity operating in an inert gas environment were investigated. According to accepted theory, the analyte has to contain electronegative functional groups in order for negative ions to be formed by the extraction of electrons from the thermionic source. This leads to a selective detector response for compounds containing nitro groups or multiple halogens. However, in the tests described here, polycyclic aromatic nitrogen hydrocarbons (PANHs), acridines, and carbazoles were used as reference substances. These compounds contain no electronegative functional groups. None of the investigated acridines exhibited any response from the detector, but carbazoles generated a strong structure-related detector response. By examining partial charges for all hydrogens of all individual carbazoles and acridine, it was demonstrated that the acidic hydrogen atom attached to the nitrogen heteroatom of the carbazoles has a strong influence on the detector response. Ionization of carbazoles may occur by dissociation of the nitrogen-hydrogen bond during contact with the thermionic surface. Support for this theory was provided by the linear relationship between the relative detector response and the deprotonization energy of the carbazoles (coefficients of determination of 0.90 and 0.98 for linear and quadratic models, respectively, were obtained). Further, there appeared to be no linear relationship between the detector response and electron affinity of the carbazoles, (R2 value, 0.32). Thus, the mechanism involved in ionization of the carbazoles is probably not direct electron transfer from the thermionic surface to the carbazoles. Principal component analysis (PCA) showed that the thermal conductivity of chemically inert detector gases also has an influence on the detector response. The investigated gases were helium, neon, nitrogen, carbon dioxide, and argon. It was found that thermal conductivity can be used to rank the detector response for the carbazoles, and there was no discernible response when helium, which has the highest thermal conductivity, was used as the detector gas.     

自供能ZnO/ZnS异质结紫外探测器的性能研究

用化学浴法在ZnO纳米棒表面沉积ZnS制备出ZnO/ZnS核壳纳米棒阵列,使用SEM、XRD和XPS等手段表征了样品的形貌、结构和成分。结果表明,ZnO/ZnS核壳纳米棒阵列表面粗糙,生长致密、分布均匀,其平均直径约为150 nm。以Pt为对电极组装的自供能ZnO/ZnS异质结紫外探测器,对紫外光具有很好的探测性能,能循环工作且性能稳定。这种探测器对微弱的紫外光也有较强的响应和较高的光敏性,且随着光强度的提高光电流密度线性增大。与自供能ZnO纳米棒紫外探测器相比,ZnO/ZnS异质结紫外探测器具有更高的响应速度,上升时间和下降时间分别提高到0.02 s和0.03 s。     

Uncooled Infrared Detector Using a Thin InAsSb Layer Acting as a Gate on a GaAs Field-Effect Transistor

The demand for high-quality low-cost uncooled infrared (IR) photodetectors have significantly increased in recent years. In this paper, a novel concept of utilizing InAsSb as a midwave IR uncooled detector is introduced. According to the approach used in this paper, the InAsSb detection layer acts as gate over a GaAs field-effect transistor (FET). IR light is absorbed in the detection layer and changes the surface potential of the transistor. The current in the transistor, which is very sensitive to those changes, should yield a sensitive detector. The same concept can be generalized to other adsorbents that absorb light at the various range of the spectrum. The advantage of using the mature technology of GaAs for achieving a low-cost efficient uncooled IR detector is clear. The experimental results presented here, using InAsSb as the absorbing layer, serve as a proof of the general concept.     

A comparison of the converging and diverging geometries for measuring enhanced backscatter

In this paper, numerical calculations are performed to compare scattered light distributions for light reflected from randomly rough surfaces in the converging and diverging illumination geometries. It is found that the enhanced backscatter peak can be measured accurately if the source and detector are at the same distance in the diverging geometry, and if the source and detector distances are approximately 100 times the size of the illuminated surface in the converging geometry.     

Highly sensitive ultraviolet detector using a ZnO/Si layered SAW oscillator

This study elucidates a highly sensitive ultraviolet light detector using the combination of an oscillator circuit with a high-frequency amplifier, a matching network and a layered surface acoustic wave (SAW) device. In this structure, a ZnO thin film is simultaneously used as an active layer for UV detection and a piezoelectric layer for exciting a high-order surface acoustic wave. The microstructure and crystallization of ZnO films were investigated using the scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The SAW oscillator shows a good performance with output power of − 1.14 dBm and phase noise of −94.7 dBc at 100 kHz. Firstly, the frequency shifts of the oscillator exhibit rapid increase with the intensity of the UV light. Then the increased shifts decayed at certain UV intensity due to the saturated photogenerated carriers. An extreme frequency shift of 1017 kHz was obtained as the UV intensity reached 551 μW/cm². The maximum sensitivity of 8.12 ppm/(μW/cm²) can be obtained in this detector.     

基于SPD的物体色快速分光测试系统设计

根据光度学与色度学理论，采用国际照明委员会（CIE）推荐的d/8标准照明／观察几何条件，应用自扫描光电二极管阵列（SPD）作为乐电探测器，设计了由积分球，脉冲光源，多色仪，光电放大与A／D转换器以及专用计算机等部分组成的双光路多通道物体表面色全光谱快速测试系统，该系统单次测色周期小于1秒，对陶瓷白板的测量精度（色度坐标）优于0．0003，重复性达到0．0001，满足了快速又准确的分光测色要求。     

A monolithic optical phase-shift detector on silicon

A novel monolithically integrated device used as an optical phase-shift detector is presented. It consists of a diffraction grating etched at the surface of a p-n photodiode fabricated by a process compatible with a standard silicon CMOS technology. When two coherent light beams are collimated toward the surface of the device, the detected optical power generates a current depending on the relative phase between the two incident beams. The operating principle of this detector and the results obtained by finite-difference time-domain modeling are presented. The fabrication process of the first devices is described and the experimental validation of the concept is demonstrated.     

Mueller-matrix ellipsometry using the division-of-amplitude photopolarimeter: a study of depolarization effects

A fully automated Mueller-matrix ellipsometer with a division-of-amplitude photopolarimeter as the polarization-state detector is described. This device achieves Mueller-matrix ellipsometry by measuring the Stokes parameters of reflected light as a function of the fast axis C of a quarter-wave retarder, which, in combination with a fixed linear polarizer, determines the polarization state of incident light. The reflected Stokes parameters were Fourier analyzed to give the 16 elements of the Mueller matrix. We investigated depolarization of polarized light on reflection from rough, heterogeneous, and anisotropic surfaces by obtaining measurements on rolled aluminum and plant leaves. The results demonstrate (1) a variation of degree of polarization of reflected light with the input polarization state, (2) the precision with which the measured matrices describe the depolarization results, (3) effects of surface anisotropy (rolling direction) on depolarization and cross polarization by reflection from aluminum surfaces, and (4) large values and differences in the depolarization effects from conifer and deciduous leaves. Depolarization of light reflected by the aluminum surfaces was most sensitive to the angle between the plane of incidence and the rolling direction when the incident Stokes parameters S(1), S(2), and S(3) were equal.     

极化聚合物薄膜电光系数的实时测量

提出了一种极化聚合物薄膜电光系数的实时测量方法。实验结构由耦合棱镜和依次制备在棱镜底面的四层薄膜组成,这四层薄膜分别是金属层（作为上电极）、极化聚合物,缓冲层和下电极。包含导波共振角并具有一定角度的入射光线会聚于棱镜底面,然后用CCD探测拍摄反射光斑,当外加电场作用于上下电极时,就可从光斑暗线位置的变化测量极化聚合物薄膜的电光系数。在测量过程中,使用了计算机图像处理方法和光学空间滤波技术。     

A new hybrid photomultiplier tube as detector for scintillating crystals

In this work, we have attentively studied the performance of a new hybrid photomultiplier tube (HPMT) as detector for photons from scintillating crystals. The HPMT is equipped with a YAP window in order to improve light collection and increase measured light response from scintillating crystals. Several measurements have been performed on BGO, LSO, CsI(Tl) and NaI(Tl) planar crystals having three different surface treatments as well as on YAP : Ce and CsI(Tl) matrices. Such crystals have been coupled to two HPMTs, one equipped with a YAP window (Y-HPMT) and the other with a conventional quartz window (Q-HPMT). Measurements on crystals coupled to the Y-HPMT have shown a consistent improvement of the light response, thanks to the presence of the YAP window. Indeed, the light response measured with the Y-HPMT was on average equal to 1.5, 2.1 and 2.6 times that obtained with the Q-HPMT for planar crystals with white painted (diffusive), fine ground and polished rear surfaces, respectively. With regards to crystal matrices, we measured a light response increase of about 1.2 times.     

Surface modification using a commercial triple quadrupole mass spectrometer

We report instrumental modifications to a commercial mass spectrometer that allow surface modification experiments to be performed using low-energy (electronvolt range) mass-selected ion beams. The design of the detector housing allows placement of the surface on the ion optical axis and some distance beyond the off-axis detector. Manipulation of the potentials applied to the final lens, detector housing, conversion dynode, and electron multiplier allow the ions to pass through the detector housing and impinge upon the surface without loss of the normal mode of detector operation. Ex situ analysis of the modified surface is performed using a home-built multisector mass spectrometer. The ability to modify organic thin films is demonstrated by a number of soft landing and surface modification experiments including (i) soft landing of (CH3)2SiNCS+ ions formed from trimethylsilyl isothiocyanate upon a fluorinated self-assembled monolayer (F-SAM) surface, (ii) soft landing and dissociative soft landing of the pseudomolecular cation of triphenylpyrylium tetrafluoroborate, viz. the triphenylpyrylium cation, upon an F-SAM surface, (iii) dissociative soft landing of 35ClCH2(CH3)2SiOSi(CH3)2+ formed from 1,3-bis(chloromethyl)disiloxane upon an F-SAM surface, (iv) surface passivation by reaction of the trimethylsilyl cation, Si(CH3)3+, with a hydroxyl-terminated self-assembled monolayer (OH-SAM), and (v) transhalogenation by reaction of CCl3+ (m/z 119) with an F-SAM surface.