Механическая сканирующая зондовая нанолитография: моделирование и применение

The paper presents a study on modeling the mechanical interaction between the tip of a scanning atomic force microscope (AFM) and surfaces of various types, which makes it possible to optimize parameters and modes for mechanical AFM nanolithography. The practical assessment of mechanical nanoprobe lithography based on the method of a direct surface patterning was carried out during fabrication of functional elements for molecular electronics. Polymethine dye nanowires of a specified configuration and the cross-section 3×20 nm have been successfully formed in a multilayer polytetrafluoroethylene/gold/silicon nanostructure.В роботі представлено моделювання механічної взаємодії вістря скануючого атомно-силового мікроскопа (АСМ) з поверхнями різних типів, що дає можливість оптимізувати параметри і режими для механічної АСМ нанолітографії. Реалізовано прототип механічної нанозондової літографії за методом прямого нанесення зображення на поверхню при виготовленні функціональних елементів молекулярної електроніки. Зокрема в багатошаровій наноструктурі политетрафторетилен/золо-то/крем¬ній сформовані нитки поліметинового барвника перерізом 3х20 нм.В работе представлено моделирование механического взаимодействия острия сканирующего атомно-силового микроскопа (АСМ) с поверхностями различных типов, что дает возможность оптимизировать параметры и режимы для механической АСМ нанолитографии. Реализовано прототип механической нанозондовой литографии методом прямого нанесения изображения на поверхность при изготовлении функциональных элементов молекулярной электроники. В частности в многослойной наноструктуре политетрафторетилен / золото / кремний сформированы нити полиметиновых красителей сечением 3х20 н

Passivation of silicon surface by ultrathin dielectric film in M/Si/nematic/ITO structures

In this work the experimental observation of passivation of silicon surface by ultrathin dielectric film in Al/Si/nematic/Indium Tin Oxide(ITO) structure performed on the base of low resistive (~ several Ωxcm) n-type conductivity silicon sample is presented. It is shown that when the DC voltage with polarity +U on silicon is applied to the structure a passivation effect of silicon surface takes place. It is found that a silicon surface passivated by dielectric film changes an initial alignment of liquid crystal 5CB. In the structure with passivating silicon surface a frequency range of structure photosensitivity extends due to limitation of current leakage through Si/liquid crystal interface. Keywords: nematic, silicon, passivation, alignment, photosensitivity, light modulator

Ultrasonic assisted nanomanipulations with atomic force microscope

Demonstrated experimentally in this work was the possibility of controlled handling the nanoparticles with the size from 50 up to 250 nm on a semiconductor surface by using an atomic force microscope under conditions of acoustic excitation. It has been shown that the selective transport of particles of a certain size is possible owing to the change of an ultrasonic vibration amplitude. Also in this study, possible mechanisms in which ultrasound may influence the particle-surface interaction and the probe-particle (surface) interaction have been analyzed

Mechanical scanning probe nanolithography: modeling and application

The paper presents a study on modeling the mechanical interaction between the tip of a scanning atomic force microscope (AFM) and surfaces of various types, which makes it possible to optimize parameters and modes for mechanical AFM nanolithography. The practical assessment of mechanical nanoprobe lithography based on the method of a direct surface patterning was carried out during fabrication of functional elements for molecular electronics. Polymethine dye nanowires of a specified configuration and the cross-section 3×20 nm have been successfully formed in a multilayer polytetrafluoroethylene/gold/silicon nanostructure

Study of Structure and Intrinsic Stresses of Ge Thin Films on GaAs

The effect of film growth rate on the structure and intrinsic stresses of thin (100 nm) Ge films grown on GaAs(100) substrates was investigate by High Resolution X-Ray Diffraction (HRXRD). The Ge films were deposited onto GaAs using thermal evaporation of Ge in the vacuum. It was shown that pseudomor-phic films with good structural quality can be obtained by this growth technique. We found out that the films have biaxial deformations due to coherent interface and Poisson ratio. The films are elastically com-pressed in the interface and stretched in the perpendicular [001] direction. The intrinsic deformations of thin Ge films strongly depended on the deposition rate. Their correlations with surface roughness, electri-cal and optical parameters are discussed. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3531

Ge/GaAs(100) Thin Films: Large Effect of Film Growth Rate and Thicknesses on Surface Morphology, Intrinsic Stresses and Electrical Properties

We found out and studied a profound effect of film growth rate on the electrical properties, intrinsic stresses and surface morphology of thin Ge films grown on GaAs(100). This effect is essential and has to be accounted for when developing and producing devices based on the Ge/GaAs heterostructure. All the Ge films under investigation were single-crystalline and epitaxially-grown on the GaAs(100) substrates. However, the transport phenomena in Ge films grown at low and high deposition rate differed drastically. Those obtained at low deposition rate were p-type and high resistant. They had a low concentration of free charge carriers and thermally activated conductivity, which is characteristic of heavily doped and strongly (in the limiting case, fully) compensated semiconductors. Although such films were single-crystalline, their conductivity was percolation-type. The Ge films obtained at high deposition rate were n-type and low resistant. They had high concentration of free charge carriers. The temperature dependence of conductivity in such films was weak or practically absent, which is characteristic of degenerate heavily doped semiconductors. Besides, the surface morphology cardinally differed for films obtained at low and high deposition rate. At low film growth rates, surfaces with developed relief were observed whose valleys and ridges formed grains of irregular shape with pronounced substructure. As the film thickness grew, the surface relief became essentially pronounced. At rather high film deposition rates, contrary to the above, the Ge film surface was fine-grained and smooth; the surface relief practically did not depend on the film thickness. As the deposition rate went down, the intrinsic stresses in films essentially decreased. The results obtained were analyzed from the viewpoint of formation of compositional and morphological inhomogeneities, and fluctuations of electrostatic potential at low growth rates. Such potential fluctuations modulate Ge energy bands leading to appearance of potential relief and deep tails of density of states in the Ge bandgap. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3506

Recrystallization processes in screen-printed CdS films

Kinetics of recrystallization in screen-printed polycrystalline CdS films has been investigated by X-ray structure analysis and optical microscopy. The relation between the crystallite size, crystallite orientation and the macrostrain, as well as their dependence on heat treatment regimes is established. It is shown that single-phase CdS films having a thickness of some tens microns, large grain size and low residual strain can be produced at optimum technological regimes. The films obtained are suitable for fabrication of CdS/CdTe solar cells

Effect of microwave electromagnetic radiation on the structure, photoluminescence and electronic properties of nanocrystalline silicon films on silicon substrate

We studied the effect of microwave electromagnetic radiation on silicon low-dimensional structures. The nanocrystalline silicon (nc-Si) films on p-Si substrate were formed with pulsed laser ablation. The surface morphology of films was studied with atomic force microscopy. We made X-ray phase analysis of films and measured strains in the structures obtained using X-ray diffractometry. We also investigated the time-resolved photoluminescence (PL) spectra and temperature dependence of photovoltage for the nc-Si/p-Si and nc- Si/p-Si structures, both before and after exposure to magnetron microwave radiation of moderate (1.5 W/cm²) irradiance. It was shown that after microwave irradiation photovoltage in the nc-Si films, as well as electron trap concentration in both the films and p-Si substrates, decrease. After irradiation of the nc-Si/p-Si structures the density of interfacial electron states (IES) decreases, while both PL intensity and relaxation time increase. At the same time irradiation of the nc-Si/p-Si structures that had high values of PL intensities and relaxation times before irradiation results in decrease of these values, as well as somewhat increases the density of IES. Higher (7.5 W/cm2) irradiance of microwave field impairs the PL properties (to the point of complete disappearance of PL). In addition it induces changes in film structure resulting, in the course of time, in decrease of strains in the structures studied. We discuss some mechanisms for microwave field effect on the properties of these structures

Light-induced mass transport in amorphous chalcogenides/gold nanoparticles composites

We have established that mass-transport processes in two types of amorphous materials, based on light-sensitive inorganic compounds like Se and As₂₀Se₈₀ chalcogenide glasses (ChG), can be enhanced at the nanoscale in the presence of localized plasmonic fields generated by visible light in gold nanoparticles (GNPs), if the condition of surface plasmon resonance (SPR) is fulfilled. It was found that irradiation by light in the presence of SPR produces profound surface nanostructurizations, and variation in topography follows closely and permanently the underlying near field intensity pattern. We have proposed a model of mass-transport in which the existence of moving anisotropic dipolar units and internal electric field in ChG as a main driving force of this movement is suggested

Laser oscillation in Cr²⁺:ZnS waveguide thin-film structures under electrical pumping with impact excitation mechanism

The laser oscillation at room temperature in Cr²⁺:ZnS waveguide thin-film structures under electrical pumping with the impact excitation mechanism was first discovered after improvement of some waveguide optical properties. However, lasing turned out to be unstable and ceases soon, which is accompanied by strong weakening the emission recorded from the waveguide edge whereas the emission from the structure face remains intensive. It is shown that the above changes stem from increasing optical losses caused by appearance of light scattering in the structure by inhomogeneities formed during lasing as a consequence the most probably of recrystallization processes in the Cr:ZnS film. Some ways are proposed to improve the lasing stabilit