Difference in charge transport properties of Ni-Nb thin films with native and artificial oxide

Here, we report on the properties of native and artificial oxide amorphous thin film on a surface of an amorphous Ni-Nb sample. Careful measurements of local current-voltage characteristics of the system Ni-Nb / NiNb oxide/Pt, were carried out in contact mode of an atomic force microscope. Native oxide showed n-type conductivity, while in the artificial one exhibited p-type one. The shape of current-voltage characteristic curves is unique in both cases and no analogical behavior is found in the literature. X-ray photoelectron spectroscopy (XPS) measurements were used to detect chemical composition of the oxide films and the oxidation state of the alloy components. Detailed analysis of the XPS data revealed that the structure of natural Ni-Nb oxide film consists of Ni-NbOx top layer and nickel enriched bottom layer which provides n-type conductivity. In contrast, in the artificial oxide film Nb is oxidized completely to Nb2O5, Ni atoms migrate into bulk Ni-Nb matrix. Electron depletion layer is formed at the Ni-Nb/Nb2O5 interface providing ptype conductivity

XPS Study of Multilayer Multicomponent Films

In the paper, we propose an XPS-based quantitative method for depth profile analysis of chemical and phase composition of multi-component and multi-layer samples. The method includes: (1) new method for background subtraction accounting for depth non-uniformity of electron energy losses; (2) new method for photoelectron line decomposition into elementary peaks, which accounts for physical nature of the decomposition parameters; (3) joint solving of both background subtraction and photoelectron line decomposition problems; (4) criterion for assessing of line decomposition accuracy; (5) simple formula for layer thickness extraction for multi-element and multi-layer sample. We apply the developed method for analysis of multilayer niobium oxide and sub-oxide films before and in course of ion milling

INFLUENCE OF FLUCTUATIONS IN NON-ELASTIC LOSSES ON ENERGETICAL SPECTRA OF ELECTRONS SCATTERED WITH SOLIDS

The classification of the reflected electron spectra (RES) from semi-infinite targets at non-sliding observation angles on the basis types of the spectra by means of the complex classification parameter has been proposed. The approximated analytical formulae describing the energetical spectra of the electrons reflected from semi-infinite homogeneous targets have been found for all the basic types of RES.Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Experimental verification of the technique for calculating light scattering in turbid media and determination of the single-scattering albedo based on the spectroscopy of elastically reflected electrons

The equations of light transfer in a turbid medium and transfer equations for electrons undergoing only elastic collisions in a solid body are shown to be equivalent. The angular distributions of elastically reflected electrons were calculated using the DISORT and MDOM optical codes. The calculation data are compared with the results of experimental measurements for the angular distributions of elastically reflected electrons and with calculations according to the Monte-Carlo method. Optical codes are shown to be highly efficient in calculating the angular distributions of electrons elastically reflected from multilayer media

Determining the applicability boundaries of small-angle approximation to the radiative transfer equation for elastic peak electron spectroscopy

The nonlinear term of the radiative transfer equation is considered in the small angle approxima tion. Angular distributions of electrons elastically scattered from semi infinite Au and Be samples are calcu lated. The error introduced by calculating flows of electrons elastically scattered from a semi infinite target in the small angle approximation is estimated

On the application of the invariant embedding method and the radiative transfer equation codes for surface state analysis

In our work we make an approbation of DISORT-like codes on the experimental base of electron spectroscopy. Due to the high accuracy of RTE solution algorithms the information about single–scattering albedo for electrons and inelastic mean free path of the surface layers is extracted from angular distributions of elastically scattered electrons. On the base of the invariant embedding method four integral-differential equations for the transmittance and the reflectance are derived. They are linearized and solved analytically in the small-angle approximation. Having math expressions it is easy to solve inverse problems by the fitting procedure. The expressions for the reflection function for each layer are derived. The energy scanning method for the surface analysis is developed on their base. The error of Rubin-Everhart model is obtained

An XPS method for layer profiling of NbN thin films

Layer chemical and phase profiling of niobium nitride thin films on a silicon substrate oxidized on air was performed with the help of a method designed by us. The method includes: a new method of background subtraction of multiple inelastically scattered photoelectrons considering depth inhomogeneity of electron inelastic scattering; a new method of photoelectron line decomposition into component peaks considering physical nature of different decomposition parameters; joint solution of the background subtraction and photoelectron line decomposition problems; control of line decomposition accuracy with the help of a suggested performance criterion; calculation of layer thicknesses for a multilayer target using a simple formula

Photoelectron emission for layers of finite thickness

Basic tools that describe the energy and angular distributions of photoelectrons emitted by inhomogeneous targets are presented. These are the functions of reflection and transmission, the function of photoelectron emission, the equation for photoelectron flow, and the equation for the transmission function, which describes the dynamics of the angular and energy spectra of photoelectrons when they move in the tar-get. The determining influence of the effects of multiple elastic scattering on the angular distribution of photoelectrons is shown. It is demonstrated in which way and by how much the effect of brightness body rotation, well known in optics, influences the X-ray photoelectron spectroscopy signal. Along with analytical solutions, the results of simulation of the X-ray photoelectron spectroscopy signals are presented

Study of NbN Ultra-thin Films for THz Hot-electron Bolometers

Hot-electron bolometer (HEB) mixers based on superconducting ultra-thin NbN films are largely used for THz spectroscopy for space and ground-based observations. Performance of the HEB mixers directly depends on the details of the structure and composition of thin film surface, as well as the nitrogen composition and its depth distribution. In this work, we present the study of the composition and the surface oxidation state of NbN films grown at two different temperatures and of 5 and 10 nm thickness