Matrix-assisted pulsed laser evaporation of polyfluorene thin films

Poly(9,9-dioctylfluorene) (PF8) thin films have been deposited by matrix-assisted pulsed laser evaporation (MAPLE) using a KrF excimer laser. The influence of the laser fluence (50-500 mJ/cm²) and the nature of the solvent (chloroform, toluene, tetrahydrofuran) on the films properties have been studied. The chemical composition of the deposited films was investigated by Fourier transform infrared (FTIR) spectroscopy and compared with the one of spin coated films. To investigate the effect of the deposition parameters on the optical properties of the films, photoluminescence (PL) measurements were performed. Poor structural and optical properties were observed for films deposited starting from chloroform solutions. When using toluene as solvent, the spectra characteristics improved with increasing laser fluence, while wide PL spectra were observed. The characteristic emission bands of the PF8 polymer were nicely detected for films deposited starting from a tetrahydrofuran (THF) solution. Moreover, in this last case, the PF8 structure is preserved at high laser fluences, too.     

热蒸发YbF3薄膜的机械特性

 实验研究了热蒸发YbF₃薄膜在大气中的应力和附着力。利用Veeco干涉仪,测试了各种工艺条件下单层YbF₃薄膜的应力。结果发现:YbF₃薄膜的残余应力为张应力,热应力在残余应力中的比重较大;沉积方式对薄膜应力的影响不大;薄膜应力在大气中有一个释放的过程。热处理后,YbF₃薄膜应力增大。     

Effects of N/Z on Spin Distribution of Evaporation Residue Cross Section as a Probe of Nuclear Dissipation

The spin distribution of the evaporation residue cross section of nuclei ¹⁹⁴Pb, ²⁰⁰Pb, ²⁰⁶Pb, and ²⁰⁰Os are calculated via a Langevin equation coupled with a statistical decay model. It is shown that with increasing the neutron-to-proton ratio (N/Z) of the system, the sensitivity of the spin distribution to the nuclear dissipation is decreased significantly. Moreover, for ²⁰⁰Os this spin distribution is no longer sensitive to the nuclear dissipation. These results suggest that to obtain a more accurate pre-saddle viscosity coefficient through the measurement of the evaporation residue spin distribution, it is best to yield those compound systems with low N/Z.     

Computation of moisture and temperature profiles in soil—The coupled model

The coupled model has been developed in this study for moisture transport and beat exchange in soil. The model is driven by atmospheric conditions measured in a field. The concept that soil has a surface resistance to evaporation is introduced in order to relate the evaporation from surface with the vapour flux in air. With the use of this concept, the simulation results agree quite well with the measured data.     

Ge-Sb-Se硫系薄膜制备及光学特性研究

介绍了几种常见的硫系薄膜制备方法, 根据现有实验条件采用热蒸发法和磁控溅射法制备出Ge-Sb-Se三元体系硫系薄膜, 通过台阶仪测试薄膜的厚度和表面粗糙度, 计算出两种制备方法的成膜速率, 并通过X射线光电子能谱测试了两种制备方法所得薄膜与块体靶材组分的差别. 利用Z扫描技术和分光光度计测试了热蒸发法制备所得薄膜的三阶非线性性能和透过光谱, 计算出非线性折射率、非线性吸收系数和薄膜厚度等参数. 结果表明热蒸发法制备Ge-Sb-Se薄膜具有良好的物理结构和光学特性, 在集成光学器件方面很高的应用潜力.     

Influence of solvent on solution processed Cu2ZnSnS4 nanocrystals and annealing induced changes in the optical,structural properties of CZTS film

The well-known quaternary Cu₂ZnSnS₄ (CZTS) chalcogenide thin films are playing an important role in modern technology. The CZTS nanocrystal were successfully prepared by solution method using water, ethylene glycol and ethylenediamine as different solvent. The pure phase material was used for thin film coating by thermal evaporation method. The prepared CZTS thin films were characterized by XRD, Raman spectroscopy, FESEM, XPS and FT-IR spectroscopy. The XRD and Raman spectroscopy analysis revealed the formation of polycrystalline CZTS thin film with tetragonal crystal structure after annealing at 450 ^°C. The oxidation state of the annealed film was studied by XPS. A direct band gap about 1.36 eV was estimated for the film from FT-IR studies, which is nearly close to the optimum value of band gap energy of CZTS materials for best solar cell efficiency. The CZTS annealed thin films are more suitable for using as a p-type absorber layer in a low-cost solar cell.     

A black hole with quantum core

A model black hole, holding a ‘quantum core’ characterized by the Planck order matter density, is revisited here. Based on the quantum improved Newton’s potential drawn out of the loop quantum cosmology we propose a Schwarzschild class, quantum improved black hole line-element that upholds the existence of Planck-dense quantum matter core. Causality is kept preserved in this proposal. Quite in a natural way the quantum core emerges closely homogeneous in its interior matter distribution. The radius of the quantum core turns out to be necessarily proportional to one-third power of the black hole mass. Hawking process of black hole evaporation leads to a shrinking quantum core, and as the mass of black hole approaches near about the Planck mass, the rate of evaporation diminishes rapidly and eventually leaves a cold remnant having a Planck order mass. Proposed model supports the standard quantum geometrical logarithmic correction to black hole entropy-area law.     

Structural and optoelectronic properties of antimony tin sulphide thin films deposited by thermal evaporation techniques

Thin films of SnSb₂S₄ have been prepared on glass substrate by using thermal evaporation techniques. The films were annealed in argon gas at low pressure in sealed glass ampoules at 85 °C, 150 °C, 275 °C and 325 °C. XRD of the films reveal that the low temperature annealed films are poly crystalline while the as deposited films and high annealed films are in amorphous states. There is no adequate variation in the photoconductivity response of the amorphous and crystalline phases. The transmittance of the films is low and having no transmittance below 740 nm. The band gap calculated by ellipsometry technique is in the range of 1.82–3.1 eV. The films have n-type conductivity but the film annealed at 325 °C show p-type conductivity.     

Novel techniques for the prepartion of synthetic diamond

Abstract

The objectives of this work are two fold: (1) to study the effect of using oxygen-acetylene flame grown synthetic diamond as seed crystals for the high pressure-high temperature conversion of graphite into diamond and (2) to demonstrate the ability to produce small crystallites of diamond by a simple, electron beam evaporation technique. In each case, the production of diamond from graphite was confirmed.     

Influence of 120 MeV Si9+ ion irradiation on ZnTe semiconductor thin films

ABSTRACT

ZnTe (Zinc Telluride) is a potential semiconducting material for many optoelectronic devices like solar cells and back contact material for CdTe-based solar cells. In the present study, ZnTe thin films were prepared by thermal evaporation technique and then irradiated with 120?MeV Si⁹⁺ ions at different fluences. These films are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Visible spectroscopy techniques. XRD study confirms increased crystallinity and grain growth for post-irradiated ZnTe thin films for fluences, up to 1?×?10¹¹ ions cm^?2. However, the grain size and crystallinity decreased for higher fluence-exposed samples. SEM images confirm the observed structural properties. Modification of the surface morphology of the film due to the ion irradiation with different fluences is studied. Optical band gap of film is decreased from 2.31?eV (pristine) to 2.17?eV after irradiation of Si⁹⁺ ions.