Der Zerfall des93Sr

Optical transmission, reflexion and absorption of thin films of the alkali metal rubidium were measured as a function of thickness for ∥ and ⊥ polarised monochromatic radiations having wavelenghts between 3000 and 6000 Å, incident from the vacuum side as well as from the quartz-support side at angles of 45 ° and 30 ° resp. The films were prepared by evaporation in static ultrahigh vacuum (～ 10^?10 Torr) onto a cooled (90 °K) smooth surface of a thin, plane-parallel plate of polycrystalline quartz. The thickness of the slowly condensing films was varied continuously from zero to some thousand Angström-units corresponding to the bulk metal. The results obtained permit the identification of the volume- or the surface-character of the different plasma oscillations and, in the latter case, the surface they are attached to, the determination of their resonance frequency and a quantitative analysis of their developement with increasing film thickness.     

FMR studies in compositionally modulated Co-Nb and Co films

Compositionally modulated (CM) films of Co-Nb have been prepared by sequential evaporation onto Si substrates using two E-guns fitted in an UHV system. The thickness of the Co sublayer was varied in the range 50 to 105 Å and that of Nb in the range 18 to 90 Å. A single layer Co film of about 850 Å was also prepared and studied. Magnetization was measured using a VSM at 290 K. FMR was observed at about 9.8 GHz in the range 3 to 290 K. For Co a layer thickness of 50 Å the magnetization in CM film is about 12% lower at 4.2 K, as compared to the bulk value. The FMR spectrum of single layer Co film shows a single absorption in the perpendicular configuration with a narrow line width of 40 Oe. Other properties of this film agree with those published in the literature. In CM films, multiple absorption modes are observed. A small perpendicular anisoropy is also measured. The magnetization in all the samples varies at T^3/2. The Curie temperature of CM films is lower than that of bulk Co. The resonance line width in CM films at lower temperatures, increases much faster than in Co film.     

Hydrogen permeation of tungsten phosphate glass thin films

Thin films of tungsten phosphate glasses were deposited on a Pd substrate by a pulsed laser deposition method and the flux of hydrogen passed thorough the glass film was measured with a conventional gas permeation technique in the temperature range 300–500 °C. The glass film deposited at low oxygen pressure was inappropriate for hydrogen permeation because of reduction of W ions due to oxygen deficiency. The membrane used in the hydrogen permeation experiment was a 3-layered membrane and consisted of Pd film (~ 20 nm), the glass film (≤ 300 nm) and the Pd substrate (250 µm). When the pressure difference of hydrogen and thickness of the glass layer were respectively 0.2 MPa and ~ 100 nm, the permeation rate through the membrane was 2.0 × 10^? 6 mol cm^? 2 s^? 1 at 500 °C. It was confirmed that the protonic and electronic mixed conducting glass thin film show high hydrogen permeation rate.     

Structural and dc conduction studies on PbTe thin films

Lead Telluride (PbTe) films of different thickness were prepared onto precleaned glass substrates under the pressure of 2?×?10^?5 Torr by thermal evaporation. X-ray diffraction technique, scanning electron microscopy, and current–voltage characteristics were used to characterize the films. The structural analysis of the films was carried using X-ray diffractometer. The surface morphology was analyzed by using scanning electron microscope. The dc electrical conduction mechanism in vacuum-evaporated Al/PbTe/Al thin film sandwich system in the thickness range 500–5,000 Å at different temperature (303–483 K) was found to be a modified Poole–Frenkel type. The results of variation of activation energy with applied voltage and thickness are discussed.     

Excitation of projectile Rydberg states in the collisions Be+-He and Mg+-He, 10–75 keV

The photoabsorption coefficient of molecular oxygen has been measured at 1215.70 Å and in the ranges 1205 Å–1214 Å and 1218 Å–1225 Å with an average resolution of ±0.015 Å. The light source in this experiment was the Doppler shifted radiation obtained from Stark quenching of a metastable hydrogen beam with energies between 2 keV and 60 keV. Using observation angles of 45°, 90°, and 135° with respect to the beam the above mentioned tuning ranges are obtained. Our data join smoothly to those of Ogawa [1] in the range 1214 Å–1218 Å and are in fair agreement with earlier measurements in other laboratories. Analytical expressions for the absorption coefficient for use in geophysical applications are presented for the whole wavelength range 1205 Å–1225 Å. Rotational structure of the absorption coefficient in the range 1220 Å–1223 Å arising from the 3-0 band of theα ¹ ∑ _u ⁺ -X ³ ∑ _g ^? forbidden transition in molecular oxygen is clearly resolved in the present measurements. A transition probability ofA=4×10⁴ s^?1 is obtained for this system. A careful study of a possible pressure dependence of the absorption coefficient was made. Except from the region were rotational line absorption occurs and the single point at 1215.70 Å no measurable effect was found for pressures below 100 Torr.     

Interfacial reactions of rf-sputtered TiNi thin films on (100) silicon with a SiN diffusion barrier

Silicon nitride (SiN) with a 50?nm thickness on Si(100) as a thermal barrier was obtained by plasma-enhanced chemical vapour deposition (PECVD). TiNi thin films were rf sputtered on a SiN/Si substrate and then annealed at 400–700°C for 30?min. Their interfacial reactions were studied using transmission electron microscopy, X-ray diffraction and Auger electron spectroscopy analyses. Experimental results show that the thickness of reaction layer in TiNi/SiN/Si specimens is clearly reduced, compared with that in TiNi/Si specimens under the same annealing conditions. The significant effect of the SiN layer as a diffusion barrier in TiNi/SiN/Si can be recognized. N and Si atoms diffuse from the SiN layer to react with TiNi films at 500°C and 600°C respectively. The TiN_{1 ? x} phase is formed in specimens annealed at 500°C, and mixed Ti₂Ni₃Si and Ti₄Ni₂O compounds are found at 600°C. In the specimen annealed at 700°C, the reaction layer has sublayers in the sequence TiNi/Ti₄Ni₂O/Ti₂Ni₃Si/TiN_{1 ? x} /SiN/Si. The SiN thermal barrier obtained by PECVD caused quite different diffusion species to cross the interfaces between TiNi/SiN/Si and TiNi/Si specimens during the annealing.     

Characterization of vacuum evaporated In - Se thin films

The InSe films of different thicknesses (290–730 mm) were deposited onto glass substrates under a pressure of 3×10^?5 Torr by vacuum evaporation method. The composition (In=53.50%, Se=46.50%) of this film was confirmed using Auger Electron Spectroscopy (AES). Thicknesses of the deposited films have been measured using a Multiple Beam Interferometry. The amorphous nature of the film is confirmed with X-ray diffractogram. From the transmittance spectra in the range of 500 nm-1200 nm, it is observed that the film showed direct allowed transition. Effect of thickness on the optical parameters such as the fundamental band gap, absorption constant, refractive index of InSe thin films are reported. Under low electric field (～ 1.5×10⁵ Vcm^?1), the results of DC conductivity measurements revealed that the variable range hopping is the dominant conduction mechanism. The values of localized states density, localization radius and hopping energy of this film are estimated as 5.57×10²⁰ cm^?3eV^?1, 0.84 Å and 0.247 eV, respectively.     

Study of preparation of Au-LiF-Au and Al-LiF-Au systems by vacuum evaporation

The structure of thin LiF film has been investigated with regard to its continuity in Au-LiF-Au, Al-LiF-Au systems. The samples have been evaporated on unheated glass substrates at 5×10^?5 torr without breaking vacuum. The number of short-circuited samples was evaluated in dependence on the angle of evaporation and thickness of the LiF film. It appears that the angle of evaporation of the value about ofω=20° already increases the number of short circuits in the case of Au-LiF-Au, meanwhile in the case of Al-LiF-Au it has no influence. Explanation is given by means of shadow effects which take place in thin LiF film in the system Au-LiF-Au. Replicas of LiF on Au and LiF on Al show in the first case that the layer consists of larger crystals and is less homogeneous. Difference between systems mentioned above can be seen also from the dependence of the number of short-circuited samples on the thickness of thin LiF film at the angle of evaporationω=0°. It is possible to draw boundary thicknesses of thin LiF film for obtaining non-short-circuited samples. In the case of Al-LiF-Au it is about 250 Å and in the case of Au-LiF-Au about 500 Å.     

Substitution mechanism of Ga for Zn site depending on deposition temperature for transparent conducting oxides

High quality transparent conductive gallium-doped zinc oxide (GZO) thin films were deposited on glass substrates using rf-magnetron sputtering system at the temperature ranging from room temperature (RT) to 500 °C. The temperature-dependence of Ga doping effect on the structural, optical and electrical properties in ZnO has been investigated. For the GZO thin films deposited at over 200 °C, (103) orientation was strongly observed by X-ray diffraction analysis, which is attributed to the substitution of Ga elements into Zn site. X-ray photoelectron spectroscopy measurements have confirmed that oxygen vacancies were generated at the temperature higher than 300 °C. This might be due to the effective substitution of Ga³⁺ for Zn site at higher temperature. It was also found that the optical band gap increases with deposition temperature. The optical transmittance of GZO thin films was above 87% in the visible region. The GZO thin films grown at 500 °C showed a low electrical resistivity of 4.50 × 10^?4 Ω cm, a carrier concentration of 6.38 × 10²⁰ cm^?3 and a carrier mobility of 21.69 cm²/V.     

Synthesis and characterization of laser ablated TiNi films

TiNi thin films with BaTiO₃ and PbZr_0.52Ti_0.48O₃ (PZT) as buffer layers were deposited on Si(100) substrates by the pulsed laser deposition (PLD) method. Buffer layers (BaTiO₃ and PZT) were deposited at 600 °C in oxygen (O₂) environment and TiNi films were deposited on the top of the buffer layer in presence of 15 mTorr nitrogen (N₂) at various deposition temperatures (50, 300, and 500 °C). Synthesis and characterization of TiNi films were investigated from the crystallographic point of view by using X-ray diffractometer (XRD) and atomic force microscope (AFM) techniques. It is found that buffer layer of BaTiO₃ and PZT have improved the crystallinity of TiNi films deposited at higher temperatures. The TiNi/PZT film was uniform compared to TiNi/BaTiO3 film with the exception of agglomerates that appeared throughout the layer.     

Optische Eigenschaften dünner Cäsium-Schichten im Wellenlängenbereich von 0,3 bis 0,9 μ und ihr elektrischer Widerstand

Electrical resistance and optical transmission, reflexion and absorption of thin films of the alkali metal cesium were measured as a function of thickness, the latter for ∥ and ⊥ polarised monochromatic radiations having wavelengths between 3000 and 9000 Å incident from the vacuum side as well as from the quartz-support side at angles of 45 ° and ca 30 ° resp. The films were prepared by evaporation in static ultra-high vacuum (～10^?10 Torr) onto a cooled (70 K) smooth surface of a thin, plane-parallel plate of polycrystalline quartz. The thickness of the slowly condensing films was varied continuously from zero to some thousand Angström-units corresponding to the bulk metal. The results obtained permit, on the one side, by means of the size effect in the resistance, the determination of the mean free path of the conduction electronsl and of the productp∞ ·l, a constant characterising fundamental electronic properties of the respectiv metal in bulk; they permit, on the other side the identification of the volume- or the surface character of the different plasma oscillations, the determination of their resonance frequency, a quantitative analysis of their development with increasing film thickness, and finally of the optical constants.     

Electrophysical parameters of <Emphasis Type="Italic">c</Emphasis>-oriented Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> films with a low concentration of antistructural defects

Epitaxial c-oriented Bi₂Te₃ films 1.2 μm in thickness are grown by the hot wall method for a low supersaturation of the vapor phase over the surface of mica substrates. The hexagonal unit cell parameters a = 4.386 Å and c = 30.452 Å of the grown films almost coincide with the corresponding parameters of stoichiometric bulk Bi₂Te₃ crystals. At T = 100 K, the Hall concentration of electrons in the films is on the order of 8 × 10¹⁸ cm^?3, while the highest values of the thermoelectric coefficient (α ≈ 280 μV K^?1) are observed at temperatures on the order of 260 K. Under impurity conduction conditions, conductivity σ of the films increases upon cooling in inverse proportion to the squared temperature. In the temperature range 100–200 K, thermoelectric power parameter α²σ of Bi₂Te₃ films has values of 80–90 μW cm^?1 K^?2.     

Characterization and electrical behavior of new lithium chalcoborate thin films

Thin films obtained with glasses of the B₂S₃Li₂S and B₂S₃Li₂SLiI systems, using a vacuum evaporation technique have been investigated. In each system, amorphous thin films and starting glasses have the same composition and similar conductivities, about 10^?4 and 10^?3Ω^?1cm^?1 respectively at 25°C. The deposition rate was in both cases 140 Å s^?1. However, a thermal treatment at 90°C of the thin films containing lithium iodide enhances the conductivity by a factor of 10 and leads to lower activation energy (0.18 eV). This behavior has been identified as a Phipps effect and can be attributed to a quick ion diffusion along thin film - substrate interface. This interfacial region was found to show unique conduction properties including a very low Li⁺ migration enthalpy.     

Effects of hydrogen flow on properties of hydrogen doped ZnO thin films prepared by RF magnetron sputtering

The hydrogen doped ZnO (ZnO:H) thin films were deposited on quartz glass substrates by radio frequency magnetron sputtering. The doping characteristics of ZnO:H thin films with varied hydrogen flow ratio were investigated. At low hydrogen flow ratio (H₂/(H₂+Ar)≤0.02), the ZnO:H thin films exhibited dominant (002) peaks from X-ray diffraction and the lattice constants became smaller. The particles were mainly a columnar structure. The particles’ size became smaller, and the island-like structure appeared on the thin films surface. In addition, the low resistivity properties of ZnO:H thin films was ascribed to the increase of the carriers concentration and carriers mobility; When the hydrogen flow ratio was more than 0.02 (M≥0.02), two absorption bands at 1400–1800 cm^?1 and 3200–3900 cm^?1 were observed from the FT-IR spectra, which indicated that the ZnO:H thin films had typical Zn–H bonding, O–H bonding (hydroxyl), and Zn–H–O bonding (like-hydroxyl). The scanning electron microscope (SEM) results show that a large number of hydroxyl agglomeration formed an island-like structure on the thin films surface. The absorption peak at about 575 cm^?1 in the Raman spectra indicated that oxygen vacancies (V_O) defects were produced in the process of high hydrogen doping. In this condition, the low resistivity properties of ZnO:H thin films were mainly due to the increasing electron concentration resulted from V_O. Meanwhile, the Raman absorption peaks at approximately 98 cm^?1 and 436 cm^?1 became weaker, and the (002) XRD diffraction peak quenched and the lattice constants increased, which shows that the ZnO:H thin films no longer presented a typical ZnO hexagonal wurtzite structure. With the increasing of hydrogen flow ratio, the optical transmittance of ZnO:H thin films in the ultraviolet band show a clear Burstein–Moss shift effect, which further explained that electron concentration was increased due to the increasing V_O with high hydrogen doping concentration. Moreover, the optical reflectance of the thin films decreased, indicating the higher roughness of the films surface. It was noteworthy that etching effect of H plasma was obvious in the process of heavy hydrogen doping.     

Conversion electron Mössbauer study of amorphous FeSi thin films

Amorphous FeSi films deposited at 77 K and at room temperature were studied by CEMS. The CEMS reflection spectra for bulk FeSi show quadrupole splittings, ΔE_S, larger by ～ 0.04 mm sec^?1 than ΔE_B - the ones shown by transmission spectra.For amorphous FeSi films ΔE was found (a) to decrease with the thickness of the film, and (b) to be by 25% larger for an amorphous film than for a crystallized one (of the same thickness).The crystallization was found to start at 240°C for a 300 Å thick film.     

Investigation of the temperature dependence for the spectra of supercooled water in the middle infrared

The temperature dependence of the bending ν₂, combination ν₂ + ν _L , and stretching (ν₁, ν₃, 2ν₂) absorption bands in the infrared spectra of supercooled water with a temperature-change step Δt from 2 to 2.5°C was studied using an advanced infrared Fourier spectrometer. It was found that the frequency of the maximum of the stretching absorption band (2700–3700 cm^?1) decreases with the reduction of the water temperature from ?0.5 to ?5.0°C. The frequency of the maximum of the combination absorption band (2130 cm^?1) increases with the reduction of the water temperature in a range from ?3.0 to ?5.0°C. The frequency of the maximum of the absorption band of bending oscillation (1640 cm^?1) is invariable with a reduction of the water temperature from ?0.5 to ?5.0°C.     

Structural and electrical properties of CdSexTe1−x thin films

The ternary semiconductors compounds are found to be very useful in the fabrication of thin film devices. This paper reports the preparation of CdSe_xTe_1?x films (1 ? x ? 0) in the thickness range 1000–3000 Å by vacuum evaporation technique onto glass and mica substrates held at temperatures, 303 to 623 K in a vacuum better than 5 × 10^?6 torr. The films were characterised by determining their composition and structure. The structure of the films, examined using XRD and TEM techniques, was found to be cubic (zincblende) in the entire composition range. The electrical resistivity and Hall mobilities have been determined as a function of film composition and deposition temperature.     

a-Si:H/a-SiNx:H超晶格薄膜光致发光性质的研究

本文报道了a-Si:H/a-SiNx:H超晶格薄膜光致发光某些性质的研究。实验发现,这种超晶格薄膜光致发光的强度和峰值能量随交替层a-Si:H厚度,测量温度及光照时间等而变化。同时还发现,在阴、阳两极上,利用GD法沉积的样品,发光强度和峰值能量也有所不同。文中对这些实验结果作了初步解释。     

Einfluß adsorbierter Gase auf Supraleitung und elektrische Leitfähigkeit dünner Thalliumschichten

Some effects of adsorbed gases on superconductivity and normal electrical conductivity of thallium films have been investigated. These films were 50 to 700 Å thick and were produced by condensation of thallium vapor on a crystalline quartz, plate at about 100 °K. At 3 °K adsorbed oxygen lowers the transition temperature and slightly increases the residual resistance. Heating of the film results in a steep increase of resistivity at about 15 °K and shifts the transition temperature to a considerably higher value. The changes in electrical conductivity and transition temperature increase with decreasing film thickness. With the thinnest films, the resistivity increases up to 50 per cent. The maximum shift of the transition temperature is 0·3 degrees. From the resistivity behavior, it can be inferred that the adsorbed oxygen molecules accept conduction electrons at 15 °K, thus changing the kind of their bond. This shows up in a decrease of the effective film thickness by 5 to 10 Å. Further, results of adsorption experiments with hydrogen, nitrogen and argon are reported. These results depend to a great extent on the purity of the gases.