A convenient ultrasonic irradiation technique for in situ synthesis of zinc sulfide nanocrystallites at room temperature

Nanocrystalline ZnS has been synthesized using a sonochemical reaction of a mixed solution of Zn(NO₃)₂, Na₂S₂O₃ and (CH₃)₂(OH)CH in Ar under ambient conditions. Detailed investigations with X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are reported. It was found that phase-pure ZnS nanocrystallites were produced, and the ZnS nanoparticles were about 6.5 nm in size, as indicated by TEM observation. The chemical mechanism for the formation of ZnS nanocrystals is discussed. This convenient method is found to be an efficient way to produce other chalcogenides as well. PACS 81.05.Dz; 81.05.Ys; 81.20.Zx     

In situ investigation of ferromagnetism in magnetic nanolayers at room temperature

Ultrathin iron layers on different substrates and a Dy_{1 ? x} Ni _x /Nibilayer have been investigated in situ using the magneto-optical Kerr effect. Ferromagnetic ordering in the Dy_{1 ? x} Ni _x /Nistructure at room temperature has been established. A technique for estimating the thickness of the iron/silicon interface is proposed.     

A novel femtosecond-laser formation of CdS nanocrystallites in zirconia matrices

A novel method for direct laser writing of two-dimensional cadmium sulfide (CdS) semiconductor nanoparticle microstructures is reported. A two photon or a higher-order multiphoton absorption process, originating from femtosecond laser pulses, was used to decompose CdS precursors dispersed in a zirconia thin film previously dip-coated on a glass substrate. The kinetics of nanoparticle formation as a function of laser power were monitored in situ by photoluminescence spectroscopy. Raman spectroscopy was also performed to characterize the structural changes of the zirconia matrix under irradiation and to verify the formation of CdS nanoparticles. Results show that CdS nanoparticles were formed by two-photon absorption (TPA) with or without the help of an additional carbazole photoinitiator.     

Experimental evidence for ice formation at room temperature

The behavior of water under extreme confinement and, in particular, the lubrication properties under such conditions are subjects of long-standing controversy. Using a dedicated, high-resolution friction force microscope, scanning a sharp tungsten tip over a graphite surface, we demonstrate that water nucleating between the tip and the surface due to capillary condensation rapidly transforms into crystalline ice at room temperature. At ultralow scan speeds and modest relative humidities, we observe that the tip exhibits stick-slip motion with a period of 0.38+/-0.03 nm, very different from the graphite lattice. We interpret this as the consequence of the repeated sequence of shear-induced fracture and healing of the crystalline condensate. This phenomenon causes a significant increase of the friction force and introduces relaxation time scales of seconds for the rearrangements after shearing.     

In situ electron beam irradiated rapid growth of bismuth nanoparticles in bismuth-based glass dielectrics at room temperature

In this study, in situ control growth of bismuth nanoparticles (Bi⁰ NPs) was demonstrated in bismuth-based glass dielectrics under an electron beam (EB) irradiation at room temperature. The effects of EB irradiation were investigated in situ using transmission electron microscopy (TEM), selected-area electron diffraction and high-resolution transmission electron microscopy. The EB irradiation for 2–8 min enhanced the construction of bismuth nanoparticles with a rhombohedral structure and diameter of 4–9 nm. The average particle size was found to increase with the irradiation time. Bismuth metal has a melting point of 271 °C and this low melting temperature makes easy the progress of energy induced structural changes during in situ TEM observations. This is a very useful technique in nano-patterning for integrated optics and other applications.     

Patterning and photoluminescence of CdS nanocrystallites on silk fibroin fiber

CdS nanocrystallites could be formed and assembled into nanoparticle strings and hexagons on natural silk fibroin fiber (SFF) through a room-temperature bio-inspired process. Herein, the biomaterial SFF served as reactive substrate, not only provides the in situ formation sites for CdS nanocrystallites, but also directs the arrangement of nanocrystalline CdS simultaneously. The photoluminescence (PL) of the resulting nanocomposites CdS/SFF is investigated extensively. The PL peaks observed from CdS nanoparticle strings are similar to those of separate CdS nanoparticles, corresponding to the band-edge emission of their individual building blocks (QD-CdS). Moreover, CdS nanoparticle hexagons perform a red-shifted and broadened emission peak.     

In situ photoemission study of the room temperature ferromagnet ZnGeP2:Mn

The chemical states of the ZnGeP(2):Mn interface which shows ferromagnetism above room temperature have been studied by photoemission spectroscopy. Mn deposition on the ZnGeP2 substrate heated to 400 degrees C induced Mn substitution for Zn and then the formation of metallic Mn-Ge-P compounds. Depth profile studies have shown that Mn 3d electrons changed their character from itinerant to localized along the depth, and in the deep region, dilute divalent Mn species (<5% Mn) was observed with a coexisting metallic Fermi edge of non-Mn 3d character. The possibility of hole doping through Mn substitution for Ge and/or Zn vacancy is discussed.     

一种实时测量和表征超薄SiO2薄膜的实验方法

采用Ｐ－偏振傅里叶变换红外反射吸收光谱技术，实现了对溅射型顺旋共振微波等离子体技术制备的超薄ＳｉＯ２薄膜的实时监测和表征。实验表明：该方法是一种无损伤性、快速而准确的实时分析ＳｉＯ２薄膜质量的有效方法。     

In situ luminescence measurement of 6H-SiC at low temperature

To understand the evolution of defects in SiC during irradiation and the influence of temperature,in situ luminescence measurements of 6H-SiC crystal samples were carried out by ion beam induced luminescence(IBIL)measurement under2 MeV H^+ at 100 K,150 K,200 K,250 K,and 300 K.A wide band(400-1000 nm)was found in the spectra at all temperatures,and the intensity of the IBIL spectra was highest at 150 K among the five temperatures.A small peak from 400 nm to 500 nm was only observed at 100 K,related with the D1 defect as a donor-acceptor pair(D-A)recombination.For further understanding the luminescent centers and their evolution,the orange band(1.79 eV)and the green band(2.14 eV)in the energy spectrum were analyzed by Gaussian decomposition,maybe due to the donor-deep defect/conduction band-deep defect transitions and Ti related bound excition,respectively.Finally,a single exponential fit showed that when the temperature exceeded 150 K,the two luminescence centers’resistance to radiation was reduced.     

The Electron-Hole plasma in CdS between 5 K and room temperature

We investigate and analyze the time-integrated nonlinear optical behaviour of an electronhole plasma in CdS as a function of the temperature and the exciting intensity. The competition between the temperature dependences of the absorption tail and of the manyparticle effects leads with increasing temperature around 160 K to a turn-over from a red- to a blue-shift of the absorption edge under excitation. The frequency dependence of the absorption for high plasma concentrations is in good agreement with theoretical calculations.     

CdS在室温热光非线性状态下的动态光谱研究

提供了一种研究半导体在光学非性状态下的动态光谱方法.将此方法应用到半导体CdS上,观察到在热光非线性状态下,其透过光谱(在吸收带边缘附近)随时间的变化(在ms数量级上).计算机模拟结果与实验相符,并得出了在CdS上获得室温光学双稳态的条件.     

Rubidium metavanadate formation at room temperature under vacuum ultraviolet irradiation from metal-organic compositions

White light emitting phosphor RbVO₃ films have been successfully fabricated by means of a vacuum ultraviolet (VUV) irradiation using an excimer lamp after spin coating of metal-organic solution onto substrates. The metal-organic carboxylates coated on substrates decomposed and reacted under the VUV irradiation. The metal-organic bonds were efficiently cleaved by the VUV illumination not only in air but also in vacuum, however, there was not a strong driving force for the reaction process to the formation of RbVO₃ in the vacuum atmosphere. On the contrary, the reaction and crystallization simultaneously proceeded under photo-chemically produced active oxygen and/or ozone atmospheres due to the VUV illumination in air. The reaction between the photo-activated Rb-O and V-O species could be strongly enhanced by the oxidation atmospheres at the moment of the metal-organic bond cleavage under the VUV irradiation.     

In beam measurements of the F colouring curves for NaCl at and above room temperature

In beam measurements have been made of the F colouring curves in NaCl between 20 and 300°C. The first colouring stage has been empirically fitted by up to three exponential components which become smaller and faster with increasing temperature. A model is presented which gives physical significance to the fitting parameters.     

Optical properties of KCP at room temperature

A fit of the reflectivity data of KCP is given using the expressions of the small polaron theory. It is further shown that small polaron theory gives the same optical properties as either a two site model with a deformation coordinate and Franck Condon transitions between the sites or a Peierls subband model for nearly free electrons.     

Hydrogen permeability of titanium at room temperature

The hydrogen permeability of titanium of grades VT1-00 and VT1-0 and of titanium iodide is investigated under saturation from glow-discharge plasma and in the cathodic process of the sulfuric acid electrolyte. A modified electrochemical method for investigating the hydrogen permeability of titanium at room temperature is proposed. Diffusion-coefficient values of hydrogen in titanium of differing purity are determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 51–54, April, 1982.     

In situ growth of CdSe/CdS quantum dots inside and outside of MWCNTs

The CdSe/CdS quantum dots were grown in situ inside and outside of the multiwalled carbon nanotubes in an innocuous solvent and at a lower temperature. The CdSe/CdS-CNTs nanoheterostructures were characterized by TEM, HRTEM, EDS, XPS and PL. The CdSe/CdS nanocrystals with diameters about 5 nm exhibit an improved PL emission.