Fortran Program for X-Ray Photoelectron Spectroscopy Data Reformatting

A FORTRAN program has been written for use on an IBM PC/XT or AT or compatible microcomputer (personal computer, PC) that converts a column of ASCII-format numbers into a binary-format file suitable for interactive analysis on a Digital Equipment Corporation (DEC) computer running the VGS-5000 Enhanced Data Processing (EDP) software package. The incompatible floating-point number representations of the two computers were compared, and a subroutine was created to correctly store floating-point numbers on the IBM PC, which can be directly read by the DEC computer. Any file transfer protocol having provision for binary data can be used to transmit the resulting file from the PC to the DEC machine. The data file header required by the EDP programs for an x ray photoelectron spectrum is also written to the file. The user is prompted for the relevant experimental parameters, which are then properly coded into the format used internally by all of the VGS-5000 series EDP packages

Comprehensive investigation of Ge-Si bonded interfaces using oxygen radical activation

In this work, we investigate the directly bonded germanium-silicon interfaces to facilitate the development of high quality germanium silicon hetero integration at the wafer scale. X-ray photoelectron spectroscopy data is presented which provides the chemical composition of the germanium surfaces as a function of the hydrophilic bonding reaction at the interface. The bonding process induced long range deformation is detected by synchrotron x-ray topography. The hetero-interface is characterized by measuring forward and reverse current, and by high resolution transmission electron microscopy. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3601355

Deep neural network for x-ray photoelectron spectroscopy data analysis

In this work, we characterize the performance of a deep convolutional neural network designed to detect and quantify chemical elements in experimental x-ray photoelectron spectroscopy data. Given the lack of a reliable database in literature, in order to train the neural network we computed a large (<100 k) dataset of synthetic spectra, based on randomly generated materials covered with a layer of adventitious carbon. The trained net performs as well as standard methods on a test set of 48500 well characterized experimental x-ray photoelectron spectra. Fine details about the net layout, the choice of the loss function and the quality assessment strategies are presented and discussed. Given the synthetic nature of the training set, this approach could be applied to the automatization of any photoelectron spectroscopy system, without the need of experimental reference spectra and with a low computational effort

On the ionization potential of molecular oxygen

The ionization potential of O2 was measured by the technique of high resolution photoelectron spectroscopy taking into account the influence of rotational structure on the shape of the vibrational bands. A value of 12.071 + or - .001 eV (1027.1 + or - 0.1 A) was found for the ionization potential. A lowering of the ionization potential caused by a branch-head when delta N = -2 gave an appearance potential for ionization of 12.068 + or - .001 eV (1027.4 + or - 0.1 A)

An XPS Investigation of Thermal degradation and Charring of Cross-linked Polyisoprene and Polychloroprene

Our interest in butadiene-containing polymers had led to an investigation of the thermal degradation of polyisoprene, PIP, and polychloroprene, PCP. The connection between cross-linking and thermal stability through an examination of PIP and PCP has been reported. Like the course of thermogravimetric analysis (TGA) the cross-linking and charring of polymers subjected to heat can also be experimentally observed as function of temperatures by the pseudo-in-situ XPS (X-ray Photoelectron Spectroscopy). Data acquisition of C1s spectra as function of temperature permits us to explore: (1) the extent of cross-linking and/or carbon accumulation of systems of PCP and PIP with/without initiators, BPO and DCP, via the analysis of the relative intensity versus temperature; and (2) the onset of charring by determining the limiting transition temperature (LTGRL) of the graphite-like structure and particularly the plasmon loss (ΔEL)

Dynamical coherent-potential approximation approach to excitation spectra in 3d transition metals

First-principles dynamical CPA (Coherent-Potential Approximation) for electron correlations has been developed further by taking into account higher-order dynamical corrections with use of the asymptotic approximation. The theory is applied to the investigations of a systematic change of excitation spectra in $3d$ transition metals from Sc to Cu at finite temperatures. It is shown that the dynamical effects damp main peaks in the densities of states (DOS) obtained by the local density approximation to the density functional theory, reduce the band broadening due to thermal spin fluctuations, create the Mott-Hubbard type bands in the case of fcc Mn and fcc Fe, and create a small hump corresponding to the `6 eV' satellite in the case of Co, Ni, and Cu. Calculated DOS explain the X-ray photoelectron spectroscopy data as well as the bremsstrahlung isochromat spectroscopy data. Moreover, it is found that screening effects on the exchange energy parameters are significant for understanding the spectra in magnetic transition metals.Comment: To be published in Phys. Rev.

Position dependent photodetector from large area reduced graphene oxide thin films

We fabricated large area infrared photodetector devices from thin film of chemically reduced graphene oxide (RGO) sheets and studied their photoresponse as a function of laser position. We found that the photocurrent either increases, decreases or remain almost zero depending upon the position of the laser spot with respect to the electrodes. The position sensitive photoresponse is explained by Schottky barrier modulation at the RGO film-electrode interface. The time response of the photocurrent is dramatically slower than single sheet of graphene possibly due to disorder from the chemically synthesis and interconnecting sheets