Conversion electron Mossbauer spectra of very thin gold films

Conversion electron Mössbauer spectroscopy of the 77.3 keV transition in¹⁹⁷Au is shown to be three orders of magnitude more sensitive than the usual gamma-ray transmission technique. CEMS spectra of metallic gold films as thin as 10–100 μg/cm² (i.e. 5–50 nm) were measured.     

利用光学方法测量薄膜厚度的研究

介绍了测量固体薄膜厚度的光学方法。分析了这些方法的光学原理,对所使用的光源、测量范围、测量精度、实现的难度以及方法所适用的场合等多种因素进行了比较分析,结果表明:对于厚度在10～100μm范围的固体薄膜而言,激光干涉法是一种简单、易于实现且测量精度较高的方法。     

Oscillations of the electrical conductivity with film thickness in very thin platinum films

Platinum films which were approximately amporphous were prepared onto glass substrates by e-gun evaporation under UHV conditions. Determination of the surface roughness showed they were smooth on atomic scale. These films fulfilled the conditions for observation of the quantum size effect (QSE) in metal films. Oscillations of the conductivity with increasing film thickness were observed during evaporation in the thickness interval from 0.5 to 2.5 nm.     

Binary separation in very thin nematic films: thickness and phase coexistence

The behavior as a function of temperature of very thin films (10 to 200 nm) of pentylcyanobiphenyl on silicon substrates is reported. In the vicinity of the nematic-isotropic transition we observe a coexistence of two regions of different thicknesses: thick regions are in the nematic state while thin ones are in the isotropic state. Moreover, the transition temperature is shifted downward following a 1/h(2) law ( h is the film thickness). Microscope observations and small-angle x-ray scattering allowed us to draw a phase diagram which is explained in terms of a binary first-order phase transition where thickness plays the role of an order parameter.     

On the possibility of measuring the electron spin in an inhomogeneous magnetic field

It is widely held that Bohr has shown that the spin of a free electron is not measurable. We point out that Bohr's argument has some important ifs and buts. A concrete configuration is calculated to produce a clear spin separation. This is then shown not to contradict Bohr's reasoning.     

On the dominant transport mechanism in very thin dielectric films

It is shown that the ratio between tunneling and Schottky thermionic emission currents in MIM structures exhibits a minimum at an applied voltage determined by the structure parameters. For appropriate parameters, the dominant transport mechanism can change from tunneling to Schottky thermionic emission and back to tunneling with increasing applied voltage.     

On the electron emission from evaporated thin Au films

Au films with island structure simultaneously show electroluminescence and electron emission. One component of the latter orginate from hot electrons, the other from field effect.     

Methods for quantitative electron probe microanalysis of small particles and thin films

The application of the electron probe microanalyzer to quantitative determination of the thickness and composition of thin films and the composition of small particles is described. The key element in these applications has been the development of accurate predictive models for the depth distribution of X-ray production (θ(ϱz) curves). The sensitivity for most elements in the periodic table is less than one monolayer based on modest electron beam currents and analysis times. By measuring intensities as a function of electron energies, the determination of concentration gradients is also possible.     

Inelastic electron tunneling spectroscopy on MOS structures with very thin oxide films

Inelastic electron tunneling spectroscopy at 4.2 K was used to investigate the defect structure of MOS capacitors with very thin SiO₂ films. Samples were degeneratelyP-andB-doped Si substrates, oxidized in O₂ at 600°C and provided with evaporated Pb, Au, In, Al or Mg electrodes. The observed peaks in the second derivative of theI-U characteristic were assigned to the excitation of phonons and of vibrational modes of the dopants and impurities. The results were found to correlate with infrared data. In addition, a distinct effect of Si/SiO₂ interface states on the characteristic was found.     

Screening in very thin films

Screening in very thin ideal metallic films is studied within the framework of the random phase approximation. In the limit of vanishing film thickness, screening is drastically reduced, from an exponential form a power form (r ⁻³). Friedel oscillations are damped byr ⁻² rather thanr ⁻³. With the help of the screened potential, effective mass, specific heat, collision times and paramagnetic susceptibility of the electron gas are estimated.     

Photochemistry on thin metal films: probe of electron dynamics in metal-semiconductor heterosystems

The surface photochemistry of on ultrathin epitaxial Ag films on Si(100) substrates has been studied with the goal to employ it as a tool to unravel the electron dynamics in such films. An increase of the photodesorption cross section is observed--a factor of 5 for 266 nm light and 12 nm film thickness--when the film thickness is decreased, despite the fact that the optical absorbtivity decreases. The increased photodesorption cross section is interpreted to result from photon absorption in the Si substrate producing electrons at energies and parallel momenta which are not allowed in Ag. These electrons penetrate through the Ag film despite the gap in the surface projected band structure utilizing quantum resonances.     

On the possibility of measuring the temperature by the luminescence of a probe with intramolecular proton transfer

The temperature dependences of the fluorescence characteristics of three forms (normal, tautomeric, and anionic) of 3-hydroxyflavone in methanol upon selective excitation in different UV ranges are studied. The fluorescence of all the forms undergoes temperature quenching, whose efficiency depends on the excitation energy. It is found that the intensity ratio of the fluorescence of different forms also varies with temperature; the excitation regions in which these variations are most pronounced are determined. The highest temperature sensitivity is observed for the luminescence intensity ratio of the normal and tautomeric forms upon excitation in the region of 280 nm, this ratio continuously increasing from 0.5 to 1.0 in the temperature range of 20–70°C. The dependence found allows one to measure the temperature of the solution in some temperature regions with an error of ～1 ± 0.5% with the help of a standard Hitachi F-2500 spectrofluorimeter.     

On the possibility of measuring the mass of the neutrino with a low energy electron beam

The neutrino mass sensitivity of the cross section just above threshold in the reaction \(_Z^A X(\bar e,v_e )_{Z - 1}^A X\) is investigated. By general arguments we find the ₃₄ ⁷⁷ Se and ₅₁ ¹²¹ Sb as the most appropriate candidates for and eventual experiment.     

On thickness dependence of electrical and optical properties of Te thin films

Received: 1 July 1997/Accepted: 6 August 1997     

nm量级薄膜厚度测量

 为了获得nm量级薄膜样品的精确厚度,采用软X射线反射率拟合方法、Bragg衍射方程方法和反射率Fourier变换方法分析了常规Cu靶X射线衍射数据及软X射线反射率数据。对厚度测量结果进行比较,3种方法得到的结果一致性很好。其中,软X射线反射率拟合和Bragg衍射方程方法精度很高,优于1 nm,Fourier变换方法精度稍低。对于单层W薄膜样品,3种方法获得厚度分别为(15.21±0.60) nm,(14.0±1.0) nm和(13.8±1.5) nm;对于双层W/C薄膜样品,W层厚度分别为(12.64±0.60) nm,(13.0±1.0) nm和(13.9±1.5) nm。这3种方法测量结果精度主要取决于反射率数据测量精度,而Fourier变换方法精度随着能量升高而提高,随着掠入射角范围增大而提高。     

nm量级薄膜厚度测量

为了获得nm量级薄膜样品的精确厚度,采用软X射线反射率拟合方法、Bragg衍射方程方法和反射率Fourier变换方法分析了常规Cu靶X射线衍射数据及软X射线反射率数据。对厚度测量结果进行比较,3种方法得到的结果一致性很好。其中,软X射线反射率拟合和Bragg衍射方程方法精度很高,优于1 nm,Fourier变换方法精度稍低。对于单层W薄膜样品,3种方法获得厚度分别为(15.21±0.60) nm,(14.0±1.0) nm和(13.8±1.5) nm;对于双层W/C薄膜样品,W层厚度分别为(12.64±0.60) nm,(13.0±1.0) nm和(13.9±1.5) nm。这3种方法测量结果精度主要取决于反射率数据测量精度,而Fourier变换方法精度随着能量升高而提高,随着掠入射角范围增大而提高。     

A new method for measuring refractive index and thickness of liquid and deposited solid thin films

We discuss theoretically a new method to determine the refractive index and the thickness of thin films using them as leaky waveguides. It is shown that the refractive index and the thickness can be determined easily by measuring the propagation constants of two leaky modes of this waveguide by means of synchronous angles. Experimentally we measured the refractive index of 1-bromonaphthalene and methylene iodide. This method is not restricted to special liquid and solid materials.     

Method of the ratio of envelopes of the reflection spectrum for measuring optical constants and thickness of thin films

A spectrophotometric method is proposed that uses the ratio of envelopes of minima and maxima of the interference reflection spectrum for measuring optical constants of a film on a substrate. Because this ratio does not contain the instrumental function of a spectrophotometer, there is no need in careful calibration of the spectrophotometer. In the case of a transparent isotropic film on an absorbing substrate, the inverse problem has an analytic solution. A simple method is proposed for numerical calculations of the optical constants and thickness of an absorbing film.