用于高速摄影变象管的软X射线光电阴极

光阴极由衬底(包括介质阴极的导电基底)和光电发射膜构成。采用了聚丙烯、Formvar和Paylene三种有机薄膜作阴极衬底。建立了这些薄膜的制备技术。用一台自制的软X射线单色仪在277—7469ev光子能量范围内测量了这些薄膜的透过率。 研究了CsI、CsBr、Au和MgF₂四种光电阴极的光电发射特性和光电发射与阴极厚度的关系,找出了最佳阴极厚度。用软X射线单色仪在277—7469ev光子能量范围内测量了最佳厚度阴极的绝对量子效率,四种阴极最大值分别为4.50、2.90、0.25和0.12。我们还在同一阴极衬底上分区制备了四种阴极,在变象管荧光屏上比较其亮度,结果和测量的一致。 用LAB5型表面分析仪对CsI和Au阴极的光电子初能量分布作了测量,CsI阴极光电子初能量分布半高宽远小于Au。因此CsI是适用于高速摄影变象管比较理想的软X射线光电阴极。     

Photoemission from diamond and fullerene films for advancedaccelerator applications

The photoemission properties of thin diamond and fullerene films were investigated for advanced accelerator applications, using subpicosecond laser pulses at three different wavelengths (650, 325, and 217 nm). The quantum efficiency (QE) obtained at 217 nm with a boron-doped, p-type, (111) polycrystalline diamond film (2.6·10 ^-4) was only five times smaller than the QE obtained with a mirror polished copper sample (1.3·10^-3) but more than nine times larger than the QE obtained with a pure diamond film or with natural diamond monocrystals. Similar results were obtained for the two-photon electron yields at 325 mm. The electron yields obtained with pure fullerene films were small and comparable to the ones observed with the pure diamond samples. With 650 mn pulses, the damage threshold of the (110) Type IIa natural diamond monocrystal (9.38·10⁴ μJ cm^-2), defined here as the fluence leading to an onset of ion emission, was 25 times larger than the damage threshold for a copper sample (3.75·10³ μJ cm^-2). The damage threshold of the boron-doped sample at the same wavelength was two times larger than that of copper. Damage thresholds with 325 nm pulses were lower, and with 217 mn pulses ion emission was observed at all fluences probably attributed to ablation of surface hydrocarbon contaminants. Results show that high-quality high-boron concentration diamond films could be a good candidate for high-RF electron guns     

潮湿空气对碘化铯薄膜结构和性质的影响

采用热蒸发法在普通载玻片上制备了碘化铯(CsI)多晶薄膜,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、高阻仪、红外分光光度计研究了暴露于潮湿空气对CsI薄膜结构、电阻率及红外透过率的影响.SEM结果表明,薄膜中颗粒平均尺寸由0.36μm变为1.25μm.吸附水沿颗粒间界扩散,间界发生弯曲和移动,大颗粒吸收小颗粒质量长大.XRD分析表明,(110)晶面衍射峰强度增加,峰位向高角度移动,半高宽减少,薄膜张应力减小,趋于形成(110/220)织构,晶粒平均尺寸为25.6,28.4,45.1 nm.受潮后薄膜电阻率由1010?·cm量级减少为108?·cm量级.在3675—3750 cm-1和3560—3640 cm-1位置出现接近游离水而非液态水的红外吸收峰,观察到吸收峰的精细结构,峰分裂源于受离子偶极键影响的羟基与吸附水气液界面处悬键的伸缩振动.     

Surface structure and composition of flat titanium thin films as a function of film thickness and evaporation rate

To correlate flat titanium film surface properties with deposition parameters, titanium flat thin films were systematically deposited on glass substrates with various thicknesses and evaporation rates by electron-beam evaporation. The chemical compositions, crystal structure, surface topographies as well as wettability were investigated by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and water contact angle measurement, respectively. The films consisted mainly of TiO₂. Small percentages of Ti₂O₃ and metallic Ti were also found at the film surface using high-resolution XPS analysis. Quantitative XPS showed little differences regarding elemental compositions among different groups of films. The films were obtained by varying the deposition rate and the film thickness, respectively. XRD data showed consistent reflection patterns of the different titanium samples deposited using different film thicknesses. Without exception measurements of all samples exhibited contact angles of 80° ± 5°. Quantitative AFM characterization demonstrated good correlation tendency between surface roughness and film thickness or evaporation rate, respectively. It is important to notice that titanium films with different sizes of grains on their surfaces but having the same chemistry and film bulk structure can be obtained in a controllable way. By increasing the film thickness and evaporation rate, the surface roughness increased. The surface morphology and grain size growth displayed a corresponding trend. Therefore, the control of these parameters allows us to prepare titanium films with desired surface properties in a controllable and reproducible way for further biological investigations of these materials.     

Influence of different precursor surface layers on Cu(In<Subscript>1-x</Subscript>Ga<Subscript>x</Subscript>)Se<Subscript>2</Subscript> thin film solar cells

The properties of Cu(In_1-xGa_x)Se₂ (CIGS) thin films obtained by selenization of the precursors with different surface layers have been studied, and photovoltaic devices based on the absorbers were measured and analyzed. The devices constructed by the absorbers obtained by selenization of the precursors with CuGa-rich surface layers are improved, compared with those with In-rich surface layers. Through XRD, SEM, SIMS, illuminated J–V, QE and Raman spectra measurements, it was found that the increased Ga contents within the surface region of films and the graded Ga distribution can be realized in the selenized thin films fabricated by the precursors with the CuGa-rich surface layer. Consequently, the performances of the photovoltaic devices based on these thin films are further improved. PACS 61.72.Ss; 87.64.Jt; 68.60.Bs; 81.15.Cd; 84.60.Jt     

微柱状CsI闪烁薄膜热蒸发生长工艺

采用真空热蒸发法在石英玻璃基片上制备了具有特殊微柱状结构的碘化铯闪烁薄膜。运用扫描电子显微镜、X射线衍射仪和荧光光谱仪分别对碘化铯薄膜的形貌、结构及发光性能等进行了表征与分析。结果表明:在基片温度为260℃、沉积速率为3 nm.s-1时,所生长的碘化铯薄膜具有理想的微柱形貌、沿(110)晶面的择优取向和良好的透射性能;紫外光激发下,发射主峰为438 nm,X射线激发下,发射主峰为315nm,说明短波段发射峰需要的激发能量较高,而长波段发射峰对紫外光激发更为敏感。     

Preparation and characterization of electrodeposited SnS thin films

Tin sulfide (SnS) thin films have been deposited by electrodeposition using potentiostaic method on indium doped tin oxide (ITO) coated glass substrates from aqueous solution containing SnCl₂·2H₂O and Na₂S₂O₃ at various potentials. Good quality thin films were obtained at a cathodic potential −1000 mV versus saturated calomel electrode (SCE). The deposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). X-ray diffraction analysis shows that the crystal structure of SnS thin films is orthorhombic with preferential orientation along 〈0 2 1〉 plane. Microstructural parameters such as crystallite size, micro strain, and dislocation density are calculated and found to depend upon cathodic potentials. SEM studies reveal that the SnS films exhibited uniformly distributed grains over the entire surface of the substrate. The optical transmittance studies showed that the direct band gap of SnS is 1.1 eV. FTIR was used to further characterize the SnS films obtained at various potentials.     

自支撑CsI/PC膜及其X射线光电转换性能研究

为了获得大面积自支撑的高效率X射线光电转换材料,通过化学气相沉积和热蒸发镀膜工艺,制备出了大面积自支撑的CsI/PC膜,其中PC(聚碳酸酯)膜厚度为300nm,CsI膜厚度在100nm到1μm。通过扫描电镜、X射线衍射仪研究了镀膜速度和受潮对样品表面形貌结构的影响。利用MANSON光源的X射线对不同沉积速率和受潮程度的样品的X射线转换效率进行了研究。在北京同步辐射装置标定了样品X射线光电转换效率,其响应灵敏度峰值大于3000μA/W;将样品作为X射线光电阴极应用在X射线条纹相机上,在神光Ⅲ主机平台上获得了清晰的X射线图像。     

狭长CsI(Tl)闪烁体发光效率的研究

提出了基于狭长CsI（Tl）闪烁体和面阵CCD器件,采用光纤和光纤面板进行光耦合及传输,以扇形束线阵扫描方式实现对X射线探测与成像的工业X-CT系统探测器方案.基此,通过物理分析及数学建模,利用Matlab模拟研究了X光能量小于450 keV时狭长CsI（Tl）闪烁体的发光效率等性能指标.研究结果表明：当光电吸收截面μph和康普顿吸收截面μc分别为0.000313和0.0000295、反射层反射系数R和衬底反射系数Rs分别取0.95和0.8、荧光线性吸收系数σ取0.000222 μm－1时,得到狭长CsI(Tl)闪烁晶体的长度l、高度h和宽度w取值范围分别是926～4512 μm、242～5000 μm和242～5000 μm的结论.在此范围内,既可使闪烁晶体有较好的空间分辨率又可获得最高的发光效率.     

Structure and luminescence of CsI:Eu columnar films

Europium doped columnar films of CsI are produced by vacuum condensation. Eu²⁺ ions in the CsI:Eu films lead to the formation of a narrow (0.18 eV), intense luminescence band with a maximum at 456 nm, which is excited by x-rays, as well as by photons of various energies. The spectral and kinetic characteristics of the emission depend on the amount of activator and on the conditions under which the film is prepared and stored. The nature of the luminescence centers is determined by structural formations that contain divalent europium ions.     

XPS characterization of sensitized n-TiO2 thin films for dye-sensitized solar cell applications

TiO₂ thin films, employed in dye-sensitized solar cells, were prepared by the sol-gel method or directly by Degussa P25 oxide and their surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The effect of adsorption of the cis-[Ru(dcbH₂)₂(NCS)₂] dye, N3, on the surface of films was investigated. From XPS spectra taken before and after argon-ion sputtering procedure, the surface composition of inner and outer layers of sensitized films was obtained and a preferential etching of Ru peak in relation to the Ti and N ones was identified. The photoelectrochemical parameters were also evaluated and rationalized in terms of the morphological characteristics of the films.     

Formation of Ti and TiN ultra-thin films on Si by ion beam sputter deposition

Ultra-thin titanium and titanium nitride films on silicon substrate were obtained by ion beam sputtering of titanium target in vacuum and nitrogen atmosphere, using argon ions with energy of 5 keV and 15 μA target current. Elemental composition and chemical state of obtained films were investigated by X-ray photoelectron spectroscopy with using Mg-Kα X-ray radiation (photon energy 1253.6 eV). It was shown that it is possible to form both ultra-thin titanium films (sputtering in vacuum) and ultra-thin titanium nitride films (sputtering in nitrogen atmosphere) in the same temperature conditions. Photoelectron spectra of samples surface, obtained in different steps of films synthesis, detailed spectra of photoelectron emission from Si 2p, Ti 2p, N 1s core levels and also X-ray photoelectron spectra of Auger electrons emission are presented.     

CsI∶Tl晶体对高能X光照射量的响应关系研究

在X光探伤系统中使用效率较高的CsI∶Tl晶体作为X光转换体。CsI∶Tl晶体对X光的响应关系是精密图像处理、定量测量所需的一项重要参量,理论上已经推导了CsI∶Tl晶体对X光的响应呈现线性关系,并针对性地设计了在60Co放射源上的定量测量实验,所获数据不仅充分证明了理论推导的正确性,还证明了相应系统的这种线性关系的线性度非常好。     

X光作用下CsI:Tl晶体的转换效率研究

X光转换材料在数字辐射成像系统中具有很重要的作用,它的效率对整个系统的量子探测效率起到决定性的作用。对CsI∶Tl晶体在X光激发下的发光效率进行详细分析,根据X光在物质中的衰减和吸收规律,从理论上推导了其对X光转换效率的关系,并建立了利用CCD相机作接收系统时的图像数据的表达形式,表明该系统输出与入射X光照射量成线性关系;并在30 MeV射频加速器上进行了实验验证。     

Microstructure and surface morphology of YSZ thin films deposited by e-beam technique

In present study yttrium-stabilized zirconia (YSZ) thin films were deposited on optical quartz (amorphous SiO₂), porous Ni-YSZ and crystalline Alloy 600 (Fe-Ni-Cr) substrates using e-beam deposition technique and controlling technological parameters: substrate temperature and electron gun power which influence thin-film deposition mechanism. X-ray diffraction, scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to investigate how thin-film structure and surface morphology depend on these parameters. It was found that the crystallite size, roughness and growth mechanism of YSZ thin films are influenced by electron gun power. To clarify the experimental results, YSZ thin-film formation as well evolution of surface roughness at its initial growing stages were analyzed. The evolution of surface roughness could be explained by the processes of surface mobility of adatoms and coalescence of islands. The analysis of these experimental results explain that surface roughness dependence on substrate temperature and electron gun power non-monotonous which could result from diffusivity of adatoms and the amount of atomic clusters in the gas stream of evaporated material.     

硬X射线调制望远镜低能探测器量子效率标定

低能X射线望远镜是硬X射线调制望远镜卫星的主要载荷之一,探测器采用CCD236.探测器的量子效率会影响能谱拟合和绝对流量,有必要对其进行标定.利用~(55)Fe放射源,以硅漂移探测器为标准探测器,标定了CCD236在Mn-K_α(5.899 keV)和Mn-K_β(6.497 keV)能量点处的量子效率,此能段在Fe线附近,对X射线天文观测有重要价值.考虑探测器的分裂事例后,Mn-K_α和Mn-K_β处的量子效率分别为71%和62%.在-95—-30?C工作温度范围内,CCD量子效率与温度无关.利用CCD236的结构及实测的量子效率,不考虑沟阻影响,得到耗尽层厚度为38μm.对CCD236施加不同的电压,其量子效率基本不变,表明其在两相驱动下高低电平的耗尽层厚度相等,进而说明CCD236一直工作在深耗尽状态,其耗尽层到了外延层和衬底层边界,已达最大值.     

Physical properties of vacuum evaporated CdTe thin films with post-deposition thermal annealing

This paper presents the physical properties of vacuum evaporated CdTe thin films with post-deposition thermal annealing. The thin films of thickness 500 nm were grown on glass and indium tin oxide (ITO) coated glass substrates employing thermal vacuum evaporation technique followed by post-deposition thermal annealing at temperature 450 °C. These films were subjected to the X-ray diffraction (XRD),UV-Vis spectrophotometer, source meter and atomic force microscopy (AFM) for structural, optical, electrical and surface morphological analysis respectively. The X-ray diffraction patterns reveal that the films have zinc-blende structure of single cubic phase with preferred orientation (111) and polycrystalline in nature. The crystallographic and optical parameters are calculated and discussed in brief. The optical band gap is found to be 1.62 eV and 1.52 eV for as-grown and annealed films respectively. The I–V characteristics show that the conductivity is decreased for annealed thin films. The AFM studies reveal that the surface roughness is observed to be increased for thermally annealed films.     

用于暗物质探测实验的CsI(Tl)晶体探测器性能的实验研究

在直接测量暗物质的实验中,反冲核能量的Quenching Factor是一个重要参数.用低能X射线源对一套测量入射中子引起的反冲核能量Quenching Factor的系统进行了能量刻度,得到了这套系统的能量响应关系.PMT单光电子的发射对应于晶体中的能量沉积约为0.32keV.同时研究了不同能量的X射线引起的PMT输出电流信号的积分时间宽度与积分电荷的关系,得到最佳的PMT输出电荷收集条件.     

Effect of deposition time on structural, electrical, and optical properties of SnS thin films deposited by chemical bath deposition

The effect of deposition time on the structural, electrical and optical properties of SnS thin films deposited by chemical bath deposition onto glass substrates with different deposition times (2, 4, 6, 8 and 10 h) at 60 °C were investigated. The obtained films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and optical absorption spectra. All deposited films were polycrystalline and had orthorhombic structure with small crystal grains. Their microstructures had changed with deposition time, and their compositions were nearly stoichiometric. Electrical parameters such as resistivity and type of electrical conduction were determined from the Hall Effect measurements. Hall Effect measurements show that obtained films have p-type conductivity and resistivity values of SnS films have changed with deposition time. For allowed direct, allowed indirect, forbidden direct and forbidden indirect transitions, band gap values varied in the range 1.30-1.97 eV, 0.83-1.36 eV, 0.93-1.49 eV and 0.62-1.23 eV, respectively.     

Complex study of titanium nano-films prepared by magnetron sputtering

The oxidation of Ti films with thickness from 5 to 100 nm was performed in air at room temperature. The thickness and roughness of metal and oxide layers were determined by neutron and X-ray reflectometry. The thin titanium films were found to be oxidized to a greater depth; than the thick ones. However the metal layer was found to exist even in the thinnest (5 nm) samples, as the direct measuring of electrical resistance of the films has confirmed. The optimal parameters of titanium films utilizable in polarizing coatings of neutron optics were estimated. The AFM data on the microrelief and the phase homogeneity of the Ti nano-film surface were obtained.