Engineering topics

Pshenichnyuk, S. A.

Publications and source records attributed to Pshenichnyuk, S. A..

7 records

DOE OSTI2019

The Unoccupied Electronic States of the Ultrathin Diphenylphthalide Films on the Surface of the Highly Oriented Pyrolytic Graphite

The results of diagnostics of the atomic composition of a diphenylphthalide (DPP) film thermally precipitated in vacuum by the of X-ray photoelectric spectroscopy (XPS) method are presented. The results of examination of the unoccupied electronic states of the ultrathin DPP films with the thickness up to 10 nm on the surface of the highly oriented pyrolytic graphite (HOPG) by the total current spectroscopy (TCS) method in the energy range from 5 to 20 eV above E{sub F} are presented. In this range, the main maxima in the total current spectra are identified. The analysis of the TCS results with consideration of the theoretical calculation results has shown that the low-energy maxima observed at the energies from 6 to 7.5 eV are induced predominately by π* electron orbitals of DPP films. The values of the energy E{sub vac} in relation to E{sub F}, i.e., of the electron work function in the DPP films at the film thickness of 5–10 nm, are found experimentally at a level of 4.3 ± 0.1 eV. The negative charge transfer from an organic film to the substrate corresponds to the formation of the HOPG/DPP boundary potential barrier during the thermal deposition of the DPP film.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2019

Atomic Composition and Morphology of Thin Films of Resveratrol Deposited on Oxidized Silicon and Polycrystalline Gold Surfaces

The atomic composition of films of a polyphenol antioxidant, namely, resveratrol (RVL), with a thickness of up to 50 nm thermally deposited on an oxidized silicon surface is studied by the method of X-ray photoelectron spectroscopy (XPS). It is found that the surface area of pores in the RVL film is about 15% of the total surface area. The results of studying the stability of the RVL films when their surface is treated with Ar{sup +} ions of 3 keV under the electric current of 1 μA passing through the sample for 30 s are given. The treatment gives rise to an increase in the area of pores to 30–40%, while the ratio of the concentration of C atoms to the concentration of O atoms in the RVL film both before and after the treatment of the surface with ions does not correspond to the chemical formula of RVL molecules. Using the method of atomic force microscopy (AFM) in contact mode with a scanning area size of about 10 × 10 μm, RVL coatings deposited on the oxidized silicon and polycrystalline Au surfaces are studied. It is found that the RVL films produce grainy and porous coatings on the substrate surfaces. The typical size of grains in the sample surface plane is 150–300 nm, and the characteristic elevation reaches 30 nm.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Generation and Fragmentation of Phthalide Derivative Negative Ions

Molecules of diphenylphthalide and 3,3-diphenylphthalide-4′,4′-dicarbonic acid have been studied using the method of dissociative electron capture negative ion mass spectrometry. The mean lifetimes of negative molecular ions relative to the electron detachment have been measured. The electron affinity has been estimated in the Arrhenius approximation and calculated by the DFT B3LYP/6-31G+(d) method.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2018

Unoccupied Electron States and the Formation of Interface between Films of Dimethyl-Substituted Thiophene–Phenylene Coolygomers and Oxidized Silicon Surface

The unoccupied electron states and the boundary potential barrier during deposition of ultrathin films of dimethyl-substituted thiophene–phenylene coolygomers of the type of CH{sub 3}–phenylene–thiophene–thiophene–phenylene–CH{sub 3} (CH{sub 3}–PTTP–CH{sub 3}) on an oxidized silicon surface have been studied. The electronic characteristics have been measured in the energy range from 5 to 20 eV above the Fermi level using total current spectroscopy (TCS). The structure of the CH{sub 3}–PTTP–CH{sub 3} film surfaces has been studied by atomic force microscopy (AFM), and the atomic compositions of the films have been studied by X-ray photoelectron spectroscopy (XPS). The changes in the maximum intensities measured by the TCS method obtained from the deposited CH{sub 3}–PTTP–CH{sub 3} film and from the substrate during increasing in the organic coating thickness to 6 nm is discussed. The formation of the boundary potential barrier in the n-Si/SiO{sub 2}/CH{sub 3}–PTTP–CH{sub 3} is accompanied by the decrease in the surface work function from 4.2 ± 0.1 to 4.0 ± 0.1 eV as the organic coating thickness increases to 3 nm. The ratio of atomic concentrations C: S in the CH{sub 3}–PTTP–CH{sub 3} films well corresponds to the chemical formula of CH{sub 3}–PTTP–CH{sub 3} molecules. The roughness of the CH{sub 3}–PTTP–CH{sub 3} coating surface was not higher than 10 nm on the ~10 × 10 μm areas as the total CH{sub 3}–PTTP–CH{sub 3}-layer thickness was about 100 nm.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Density of Electronic States in the Conduction Band of Ultrathin Films of Naphthalenedicarboxylic Anhydride and Naphthalenetetracarboxylic Dianhydride on the Surface of Oxidized Silicon

The results of examination of the electronic structure of the conduction band of naphthalenedicarboxylic anhydride (NDCA) films in the process of their deposition on the surface of oxidized silicon are presented. These results were obtained using total current spectroscopy (TCS) in the energy range from 5 to 20 eV above the Fermi level. The energy position of the primary maxima of the density of unoccupied states (DOUS) of an NDCA film was determined based on the experimental TCS data and calculated data and compared with the position of the DOUS maxima of a naphthalenetetracarboxylic dianhydride (NTCDA) film. The theoretical analysis involved calculating the energies and the spatial distribution of orbitals of the molecules under study at the B3LYP/6-31G(d) DFT (density functional theory) level and correcting the obtained energies in accordance with the procedure that was proven effective in earlier studies of the conduction band of films of small conjugated organic molecules. It was found that the DOUS maxima of the NTCDA film in the studied energy interval from 5 to 20 eV above the Fermi level are shifted toward lower electron energies by 1–2 eV relative to the corresponding DOUS maxima of the NDCA film Subdivision of the Ufa Federal Research Centre of the.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2017

Atomic composition and stability of Langmuir–Blodgett monolayers based on siloxane dimer of quaterthiophene on the surface of polycrystalline gold

Atomic composition of monolayers based on siloxane dimer of quaterthiophene deposited by Langmuir–Blodgett technique on a silicon dioxide surface partially covered by gold film and the stability of these monolayers upon surface treatment by Ar{sup +} ions bombardment have been studied. Experimental results for the chemical composition of a series of studied surfaces have been obtained by X-ray photoelectron spectroscopy (XPS) by recording XPS spectra of C 1s, O 1s, S 2p, and Au 4f core levels. The relative concentration of Au and Si substrate atoms and the composition of ex situ prepared surface under study were determined within 10–15%, which indicates that Langmuir–Blodgett monolayers based on siloxane dimer of quaterthiophene form continuous coating in a considerable extent. Prior to the treatment of the studied surface by Ar{sup +} ions bombardment, carbon- and oxygen-containing surface adsorbates provided a considerable contribution to the results of XPS measurements. The surface cleaning by Ar{sup +} ions with energy 3 keV at electric current through sample of ~1 μA in several 30-s steps has led to the etching of surface adsorbates and next Langmuir–Blodgett films of the siloxane dimer of quaterthiophene.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

Electron attachment to the phthalide molecule

Phthalide, the simplest chain of conductive polymer thin film, was investigated by means of Electron Transmission Spectroscopy, Negative Ion Mass Spectrometry, and density functional theory quantum chemistry. It has been found that formation of gas-phase long-lived molecular anions of phthalide around 0.7 eV takes place through cleavage of a C–O bond of the pentacyclic ring of the parent molecular anion to give a vibrationally excited (electronically more stable) open-ring molecular anion. The energy of the transition state for ring opening of the parent negative ion is calculated to be 0.65 eV above the neutral ground state of the molecule. The energy (2.64 eV) evaluated for the corresponding transition state in the neutral molecule is much higher, so that the process of electron detachment from the anion must lead to a neutral molecule with its initial pentacyclic structure. The average lifetime of the molecular negative ions formed at an electron energy of 0.75 eV and 80 °C is measured to be about 100 μs. The known switching effect of thin phthalide films could stem from the presence of a similar open/closed transition state also in the polymer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗