Scalable fabrication of Bi_2O_2Se polycrystalline thin film for near-infrared optoelectronic devices applications

We present a controlled, stepwise formation of layered semiconductor Bi_2O_2 Se thin films prepared via the vapour process by annealing topological insulator Bi_2Se_3 thin films in low oxygen atmosphere for different reactions. Photodetectors based on Bi_2O_2 Se thin film show a responsivity of 1.7×10~4 A/W at a wavelength of 980 nm. Field-effect transistors based on Bi_2O_2 Se thin film exhibit n-type behavior and present a high electron mobility of 17 cm~2/V·s. In addition, the electrical properties of the devices after 4 months keeping in the air shows little change, implying outstanding air-stability of our Bi_2O_2 Se thin films. From the obtained results, it is evident that low oxygen annealing is a surprisingly effective method to fabricate Bi_2O_2 Se thin films for integrated optoelectronic applications.     

Near-field optical characterization of interacting and non-interacting gold nanoparticles embedded in a silica thin film

By near-field optics, we characterized the local optical properties of clusters of gold nanoparticles randomly distributed under a 50 nm-thick SiO₂ thin film. A local field enhancement is visible above isolated clusters. A few hundred nanometers away from them, we observed a polarization-dependent pattern with elliptical lobes oriented in the incident polarization direction. A simple simulation shows that the observed near-field images can be represented by the sum of the field of an oscillating dipole and the incident field. When the cluster density is larger, the measured near-field images show numerous bright and dark spots. The position of the bright spots does not necessarily coincide with the gold clusters showing the presence of coupling effects between them.     

Structure and optoelectronic properties of multi-element oxide thin film

This paper focuses on analyzing structural and optoelectronic properties of (ZnSnCuTiNb)_1 − xO_x films. The results of XRD and HRTEM indicate that the (ZnSnCuTiNb)_1 − xO_x films are all of amorphous without any multi-phase structure. XPS analysis confirms that the increase of the oxygen content makes the cations electron binding energy higher, suggesting the removal of valence electrons or the extent of oxidation can change the optoelectronic properties of the films. The (ZnSnCuTiNb)_1 − xO_x films possess the characteristics of optoelectronic semiconductor whose oxygen content are 51.6 and 56 atom%. These films have carrier concentrations of 2.62 × 10²⁰ and 1.37 × 10¹⁷ cm⁻³, and conductivities (σ) of 57.2 and 9.45 × 10⁻³ (Ω cm)⁻¹, and indirect band gaps of 1.69 and 2.26 eV, respectively. They are n-type oxide semiconductors.     

Compatibility and optoelectronic of ZnSe nano crystalline thin film

We report the room temperature synthesis of zinc selenide (ZnSe) nano crystalline thin film on quartz by using a relatively simple and low cost closed space sublimation process (CSSP). The compatibility of the prepared thin films for optoelectronic applications was assessed by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), Raman spectroscopy, photoluminescence, and Fourier transform infrared spectroscopy (FT-IR). The XRD confirmed that the films were polycrystalline with the preferential orientation along the (111) plane corresponding to the cubic phase (2θ = 27.28 ). The AFM indicated that the ZnSe film presented a smooth and compact morphology with RMS roughness 19.86 nm. The longitudinal optical phonon modes were observed at 247 cm 1 and 490 cm 1 attributed to the cubic structured ZnSe. The Zn-Se stretching band was confirmed by the FT-IR. The microstructure and compositional analysis was made with the SEM. The grain size, dislocation density, and strain calculated were co-related. All these properties manifested a good quality, high stability, finely adhesive, and closely packed structured ZnSe thin film for optoelectronic applications.     

Electron impinging on metallic thin film targets

Based on the Vicanek and Urbassek theory [M. Vicanek, H.M. Urbassek, Phys. Rev. B 44 (1991) 7234] combined to a home-made Monte Carlo simulation, the present work deals with backscattering coefficients, mean penetration depths and stopping profiles for 1-4 keV electrons normally incident impinging on Al and Cu thin film targets. The cross-sections used to describe the electron transport are calculated via the appropriate analytical expression given by Jablonski [A. Jablonski, Phys. Rev. B 58 (1998) 16470] whose new improved version has been recently given [Z. Rouabah, N. Bouarissa, C. Champion, N. Bouaouadja, Appl. Surf. Sci. 255 (2009) 6217]. The behavior of the backscattering coefficient, mean penetration depth and stopping profiles versus the metallic film thickness at the nanometric scale and beyond is here analyzed and discussed.     

有机半导体薄膜生长原位实时测量方法的研究

针对原位实时监测有机半导体薄膜生长情况的需求, 提出了差分反射光谱法与场效应晶体管法结合的光电联合测量方法, 设计研制了测量系统. 以并五苯有机分子为例, 通过自制底栅底接触式场效应管微结构, 实验测试了热蒸发法生长导电膜层过程中光电信号的演变与相互关联. 光谱信号显示, 并五苯以薄膜态结构进行生长, 光谱随生长进程变化显著. 实验数据与四相结构模型仿真结果的良好吻合, 表明因薄膜增厚引起干涉条件的改变是光谱变化的主因, 由此推算出薄膜生长速率为0.23 nm/min. 当薄膜等效厚度达到28 nm时, 场效应管的导电性显著增强, 标志着并五苯有效传输层的形成. 此后, 薄膜厚度持续增加, 但测试电流增长缓慢, 说明该结构进入电学特性饱和区. 光电联合法不仅有助于研究有机半导体薄膜的光谱信息、电学特性和薄膜结构之间的相互对应关系, 也为发展原位监测有机半导体薄膜制备过程, 探索最佳工艺提供了新的研究手段.     

Surface-plasmon-mediated single-molecule fluorescence through a thin metallic film

We demonstrate that fluorescence of single molecules in the nanometric vicinity of a thin gold film can be effectively excited and detected through the film with an epi-illumination scanning confocal microscope. A full theoretical treatment of the fluorescence signal indicates that both excitation and emission are surface-plasmon mediated. Remarkably, the number of photons detectable from chromophores perpendicular to the interface is enhanced by the presence of the metal.     

Plasmonic interactions between a metallic nanotube array and a thin metallic film

Using the finite difference time domain (FDTD) method, we numerically simulate the plasmonic interactions and the optical properties of a metallic nanotube array near a thin metallic film. We show that the energies and intensities of the plasmon resonances depend strongly on the aspect ratio (the ratio of the inner to outer radius) of the nanotube, the separation between the center of the nanotube and the upper surface of the metallic film and the thickness of the film. In the thin film limit, the high-energy localized tube-related plasmons can induce their images on both sides of the metallic film, so the degeneracy state splits into two modes. Based on the nature of the field distribution, we also show clearly the plasmon resonant characteristics that the electromagnetic fields decay away from the surface of the nanotubes and both sides of the metallic film.     

Combinatorial arc plasma deposition search for Ru-based thin film metallic glass

We have discovered a novel Ru-based thin film metallic glass (TFMG) using combinatorial arc plasma deposition (CAPD). To search for Ru-based TFMG, alloy systems of Ru-Zr-Al, Ru-Zr-Fe and Ru-Zr-Mo were investigated by making libraries. Each library consisted of 1089 CAPD samples deposited on a substrate by CAPD. Composition of each sample is different with each other.The composition and phases of the CAPD samples were measured by energy dispersive X-ray fluorescence spectrometry and X-ray diffractometry, respectively. Results showed the amorphous regions depended on the additive elements Al, Fe or Mo. Compared with the addition of Al, the addition of Fe or Mo exhibited high amorphous forming ability.To evaluate the mechanical properties, the glass transition temperature T_g and the crystallization temperature T_x of the amorphous samples in each Ru-Zr-X alloy, larger samples having the same compositions as the typical amorphous CAPD samples were reproduced by sputtering because the CAPD samples were too small to measure the mechanical properties, T_g and T_x.Ru₆₅Zr₃₀Al₅ and Ru₆₇Zr₂₅Al₈ samples were found to exhibit the better fracture stress and elastic limit than conventional TFMGs, while Ru-Zr-Fe and Ru-Zr-Mo samples were found to be brittle. DSC revealed that the Ru₆₅Zr₃₀Al₅ sample was a TFMG, with a T_g of 902 K and T_x of 973 K.     

Single-wafer optical processing of semiconductors thin insulator growth for integrated electronic device applications

This paper presents an overview of the single-wafer optical processing techniques for integrated circuit fabrication with an emphasis on their applications to insulator growth. Rapid thermal growth of various thin homogeneous and heterogeneous dielectrics on silicon substrates including silicon dioxide, silicon nitride, nitrided oxides, and composition-tailored insulators will be described and some electronic device applications of the rapidly grown dielectrics will be examined. Multicycle rapid growth processes have been used for dielectric structural engineering and in-situ formation of thin layered insulators. The compositional depth profiles and the electrical characteristics of devices are controlled through the synthesis of an appropriate sequence of the wafer temperature-vs-time profiles and process gas cycles. The ongoing developments and future prospects of single-wafer rapid processing for advanced microelectronics manufacturing will also be discussed.     

Alternative methods of identifying the oxidation of metallic nanoparticles embedded in a matrix

We compare methods for valence-state analysis based on energy-loss near-edge structure (ELNES), including the white-line ratio (WLR), pre-edge peak (prepeak) and post-edge peak (postpeak) techniques. Starting from multiple-scattering calculations, we correlate the appearance of a prepeak in the O-K edge and postpeak in the L-edge with oxidation of a transition metal (TM). The ability to use more than one technique is especially advantageous for a nanocomposite of metallic nanoparticles embedded in a matrix, as we show for the case of iron nanoparticles in a silica matrix.     

Sub-micron ablation of metallic thin film by femtosecond pulse laser

The ability to machine very small features in a material has a wide range of applications in industry. We ablated holes into thin film of 100 nm thickness made from various metals by femtosecond pulsed laser ablation. Using a Ti:Sapphire laser which supplies a laser pulse of 150 fs duration at central spectrum wavelength of 400 nm, we have produced a series sub-micron holes, whose diameters are less than 200 nm with a focused laser spot of 1.7 μm. We found that the material damage threshold has a great influence on the quality of the produced features. Experimental results shows that the heat-affected zone and the degree of being affected reduce with the increase of threshold value.     

Nanocluster n-CdO thin film by sol-gel for solar cell applications

The nanocluster-CdO film was successfully synthesized by sol-gel method using cadmium acetate and 2-metoxyethanol as starting materials and monoethanolamine as a stabilizer. The structural properties of the CdO film were investigated by atomic force microscopy (AFM). AFM results indicate that the CdO film is consisted of nanoclusters with grain size of 75-85 nm. The optical band gap E_g of nanocluster-CdO film was found to be 2.27 eV. The heterostructure, formed from two semiconductor layers having different optical band gaps, p-Si/n-CdO is prepared as a solar cell device. The electrical properties of the device were characterized by current-voltage and capacitance-conductance-voltage methods. The photovoltaic properties of p-Si/n-CdO device have been investigated. The p-Si/n-CdO heterojunction solar cell shows the best values of V_oc = 0.41 and J_sc = 2.19 mA/cm² under AM1.5 illumination. It is evaluated that this work is useful as a basis for the search of nanomaterial CdO and more competitive p-Si/n-CdO based solar cells, despite the fact that V_oc and J_sc are lower than those reported in the literature.     

An in-depth investigation of physical properties of Nd doped CdS thin films for optoelectronic applications

The different contents (0 wt.%, 1 wt.%, 3 wt.% and 5 wt.%) of Nd @CdS films were casted using spray pyrolysis deposition procedure. The preferential orientation of crystallites along (002) for all films was noted by XRD profiles. The mean crystalline size (D_avg), strain (ɛ_avg) and dislocation density (δ_avg) have also been evaluated using XRD results and discussed. The spherical shape morphology of nanoscale particles of Nd@CdS films were analyzed by FE-SEM, exhibits the increased grain sizes with Nd doping concentration. The optical band gaps (2.4–2.36 eV) were found to be decreased with increasing Nd doping content upto (3 wt.%) and increased at 5 wt.% The PL profile displays a stout intensity peak observed at 532 nm and week emission band at 638 nm. The dielectric constant, loss and loss tangent of pristine and Nd@CdS thin films were investigated by dielectric measurements. The optimum values of non-linear refractive index 1.06 × 10⁻¹⁰, 4.41 × 10⁻¹¹, 3.44 × 10⁻¹¹ and 1.85 × 10⁻¹⁰ were observed for Nd content varies from pristine to 5 wt.% respectively. Furthermore, optimum non-linear susceptibility values 7.31 × 10⁻¹², 1.079 × 10⁻¹², 4.53 × 10⁻¹³ and 1.36 × 10⁻¹¹ were observed for 0, 1, 3 and 5 wt.% of Nd contents respectively in CdS. Such type of characteristics of Nd doped CdS thin films can be useful for optical devices.     

Structural, optical and electrical properties of ZnO:Al thin films for optoelectronic applications

Undoped and aluminum-doped ZnO thin films are prepared by the sol–gel spin-coating process. Zinc acetate dihydrate, ethanol and mono-ethanolamine are used as precursor, solvent and stabilizer, respectively. The atomic percentage of dopant in solution were [Al/Zn] = 1 %, 2 % and 3 %. The effect of Al doping on the optical and electrical properties of ZnO films was investigated by X-ray diffraction (XRD), Four-Point probe technique and UV–visible spectrophotometery. The results from the X-ray diffraction show that the pure ZnO thin films had a polycrystalline structure of the hexagonal Wurtzite Type. A minimum resistivity of $3.3 \times 10^{-3} \Omega \cdot \mathrm{cm}$ was obtained for the film doped with 2 mol % Al. Optical transmissions reveal a good transmittance within the visible wavelength spectrum region for all of the films. The value of the band gap is enhanced from 3.21 eV (undoped ZnO) to 3.273 eV (Al/Zn = 3 %), the increase in the band gap can be explained by the Burstein–Moss effect.     

Optical, structural and optoelectronic properties of pulsed laser deposition PbS thin film

Lead sulfide (PbS) nano-structured film has been grown on quartz substrates by the PLD technique. The deposited films were characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Formation of cubic phase of PbS nanocrystals is proven. The absorption and emission spectra were measured for different thicknesses of the films. I–V characteristics and photoconductivity of the deposited film were also measured. The results indicate an efficient performance of the deposited films as an optical detector.     

Patterning thin metallic film via laser structured weakly bound template

A weakly bound buffer material is structured on a surface by interfering low power laser beams, as a template for patterning metallic thin films deposited on top. The excess buffer material and metal layer are subsequently removed by a second uniform laser pulse. This laser pre-structured buffer layer assisted patterning procedure is demonstrated for gold layer forming a grating on a single crystal Ru(1 0 0) under UHV conditions, using Xe as the buffer material. Millimeters long, submicron (0.65 μm) wide wires can be obtained using laser wavelength of 1.064 μm with sharp edges of less than 30 nm, as determined by AFM. This method provides an all-in-vacuum metallic film patterning procedure at the submicron range, with the potential to be developed down to the nanometer scale upon decreasing the patterning laser wavelength down to the UV range.