The opportunity of the charge-based deep level transient spectroscopy (Q-DLTS) for study of the structures based on wide bandgap semiconducting and insulating materials such as diamond and Al2O3 was demonstrated. Using our isothermal Q-DLTS method with rate window (tm)scanning we obtained information about concentration, activation energy and capture cross-section of the native and extrinsic electrical active defects - trapping centers (TC) in slightly boron-doped polycrystalline diamond, diamond single-crystal and in the structures Al2O3 film on NiFe and Si substrates. In comparison with widely used capacitance-based deep level transient spectroscopy, Q-DLTS gives one possibility to investigate the structures in which a capacitance does not depend on the charge state of the surface and bulk traps.

Measurement and calculation results are presented that confirm that design four-mirror compensators can be designed for the spectral range of 200–2000 nm that is widely used in modern spectral ellipsometers. Measurements and calculations according to standard ellipsometric programs have been carried out on a broadband LED spectral ellipsometer with switching of orthogonal polarization states. Mirrors with the structure of glass substrate/Al 2 O 3 layer (20–30 nm thick)/Al layer (150 nm thick)/upper Al 2 O 3 layer (with specified thickness d ) have been prepared by vacuum-evaporation method. It is shown that the phase-shift spectra of a four-mirror compensator, two mirrors of which have a native oxide 5.5 nm thick and the two others of which have an oxide layer 36 nm thick, measured on the ellipsometer, are flattened in comparison with similar spectra of a compensator, all four mirrors of which have a native oxide, especially in the short-wavelength spectral region. The results of calculating the phase-shift spectra of the four-mirror compensator with six variable parameters (angles of incidence of radiation on the mirrors and thicknesses of oxide layers on four mirrors) are presented. High-quality achromatization in a wide spectral range can be achieved for certain sets of parameters.

A light-emitting diode (LED) magneto-optical ellipsometer with the switching of orthogonal polarization states is described. The distinctive features of the ellipsometer are the implementation of the maximally deep azimuthal modulation, application of two-channel detector, use of a set of LEDs ensuring a high signal-to-noise ratio, and the absence of moving polarization elements. These features have substantially increased the precision of measurements of ellipsometric parameters ψ and Δ for ferromagnetic materials and their changes (δψ and δΔ) in the magnetic field, which are connected for the transverse Kerr configuration by simple relations with magneto-optical parameters. At wavelengths of 365, 372, 390, 405, 420, and 465 nm, the precision of ψ-δψ and Δ-δΔ measurements of metal films is about 0.0003° and 0.001°, respectively. The spectral resolution is 4 nm; the minimal measurement time of ψ and Δ in the continuous spectral range of 270–1000 nm is 20 s; the magnetic field is varied from–2500 to +2500 Oe; and the step of the magnetic field setting is 0.5 Oe.

Описан светодиодный магнитооптический эллипсометр с переключением ортогональных состояний поляризации, отличительными особенностями которого являются: реализация максимально глубокой азимутальной модуляции, применение двухканального детектора, использование набора светодиодов, обеспечивающих высокое отношение сигнал/шум, и отсутствие движущихся поляризационных элементов. Эти особенности позволили существенно повысить воспроизводимость измерений эллипсометрических параметров Ψ и Δ ферромагнитных материалов, а также их изменений (δΨ и δΔ) в магнитном поле, связанных для поперечной конфигурации Керра простыми соотношениями с магнитооптическими параметрами. На длинах волн 365, 372, 390, 405, 420 и 465 нм воспроизводимость измерений Ψ, δΨ и Δ, δΔ пленок металлов составила около 0.0003° и 0.001° соответственно. Спектральное разрешение равно 4 нм; минимальное время измерения Ψ и Δ в непрерывном спектральном диапазоне 270–1000 нм составило 20 с; величина магнитного поля изменяется в диапазоне от –2500 до +2500 Э; дискретность установки магнитного поля 0.5 Э.

Laser fabrication of micrometer-scale graphitic structures in the bulk of monocrystalline CVD diamond was investigated. Ultra-short (1ps) pulses of Ti:sapphire laser were tightly focused inside the sample. Initiation of graphitization in the focal volume and propagation of graphitization front towards the laser beam are considered. Electrical resistivity of the produced graphitic material was measured (3.6–3.9Ωcm). Problems and strategies of 3D laser writing are discussed paying special attention to graphitization homogeneity, minimization of the wire diameter, control of the structure shape and reduction of the surrounding diamond damage. Laser fabrication of complex microstructures including pillars, plates, hexagonal chain and periodic arrays of straight wires has been demonstrated.

Free-standing undoped polished MPCVD diamond films (200-300 mu m thick) have been used to fabricate photoconductive and photodiode structures for UV light detection. Multifinger planar Au/Cr electrodes of the photoconductive structures were realized on the diamond surface by lithographic technique. The sandwich semitransparent Ni electrodes of the photodiode structures were deposited by a magnetron sputtering on both sides of the diamond films. The films showed conductivity less then 10(-15) S/cm at room temperatures with activation energy close to 1 eV and low concentration of the electrically active defects according to charge-based deep-level transient spectroscopy (Q-DLTS). The distinct trap levels with activation energy of 0.5, 0.7 and similar to 1.3 eV were evaluated.Planar photoconductive detectors with electrodes on the growth side showed the dark current below 1 pA at 10 V bias voltage with spectral discrimination ratio higher than 5 X 10(5) (at 50 V bias) in the 210-270 nm wavelength range. Two orders of magnitude lower responsivity were found on the nucleation side. The sandwich photodiodes showed a sharp cut-off in photoresponse at 220 nm and photovoltage as high as 2.3 V in open circuit regime. (c) 2004 Elsevier B.V. All rights reserved.

Electrical transport and traps in vertical SiGe/Si QW structures of low background doping level are studied in the presented report. Temperature activation of holes from the quantum well was found to determine the vertical current through Si/SiGe/Si structures at T > 160 K. At lower temperatures (T < 130 K), the current mechanism is attributed to a thermally activated tunneling of holes from quantum well. Deep traps are observed in the Si/SiGe/Si structures in high concentration (1011 – 1012 cm-2). Traps are most likely assistance in the current in the vertical Si/SiGe/Si structures as recombination centers near the QW.

This work reports on electronic properties of nitrogen‐doped, n‐type ultrananocrystalline diamond (UNCD) films grown on p‐type Si substrates from CH4–Ar–N2 gas mixtures using a microwave plasma chemical vapor deposition technique. Films ∼1 µm thick were grown with 5%N2 and 10%N2 in the plasmas. Charge‐based deep‐level transient spectroscopy showed a shallow level of point defects with an activation energy of ∼0.05 eV. The density of these shallow defects was increased with increasing nitrogen content in the plasma. Complex scanning probe microscopy methods were applied to study the film microstructure. Generally it was found that the nitrogen‐doped UNCD films showed a periodic ‘cell‐like’ structure in which the cell with a lateral size of several nanometers was less conducting than the boundary between the cells. The boundary width was found to be 0.5–1 nm. The observed details of the periodic structure can be associated with diamond nanocrystallites (grains) and grain boundaries, respectively. In addition, 2–5 nm high‐conducting inclusions clustered on the film surface were observed. It was noted that the emission field was inversely proportional to the film electroconductivity, and the lowest emission field of F ∼ 10 V µm−1 was detected near the high‐conducting inclusions. Moreover, the surface electron potential at the emission sites was lowered. The reasons why the shallow donor center is predominantly introduced by nitrogen incorporated into the grain boundaries and the possible mechanisms of low‐field electron emission from the nitrogen‐doped UNCD films have been discussed. Copyright © 2004 John Wiley & Sons, Ltd.

A comparative study of electrically active defects has been performed for undoped and nitrogen-doped nanocrystalline diamond thin films deposited on Si substrates from CH4/Ar/H2 and CH4/Ar/N2 gas mixtures using microwave and d.c. plasma CVD techniques. The method of charge-based deep level transient spectroscopy (Q-DLTS) was applied to obtain information on the concentration, activation energy and capture cross-section of native and nitrogen-induced defects. A common feature in Q-DLTS spectra of undoped films was the presence of a deep level with the activation energy of 0.13–0.22 eV. The Q-DLTS spectra of nitrogen-doped films, however, exhibited a shallow level peak with the activation energy of approximately 0.05 eV. The density of the shallow defects was found to increase with increasing concentration of incorporated nitrogen. The photoelectrical properties of the films were also studied. The kinetics of photoresponse to a high intensity light pulse (in open circuit condition at zero bias) was measured. These photoresponse data were obtained at saturation conditions and were used for designing the energy band diagram for the p-Si/UNCD film/metal and n-Si/UNCD film/metal heterostructures studied.

The electrically active defects in the boron-doped polycrystalline and homoepitaxial CVD films and HPHT diamond single-crystal were investigated. Isothermal Charge-based Deep Level Transient Spectroscopy was applied to study the density, activation energies - E-a, and capture cross-sections of defects (trapping centers - TC) in diamond samples. It was shown that TC in polycrystalline diamond samples have a continuous energy spectrum with two or three peaks that correspond to discrete energy levels in forbidden band of diamond, while in boron-doped homoepitaxial diamond films and in single diamond crystals only one boron-induced deep level was displayed. The difference in the boron incorporation into (111) and (100) faces of single-crystals was observed as well. The activation energy of boron-induced levels decreases and TC density increases with increasing boron concentration. The activation energy E-a in highly doped diamond increases with increasing degree of compensation, whereas the difference between values of E-a and activation energy E-a(') obtained from the temperature dependence of electrical conductivity arises.

The acceptor and donor defects of thick (approx. 0.4 mm) free-standing boron and nitrogen containing microwave plasma CVD polycrystalline diamond films were investigated. Charge-based deep level transient spectroscopy (Q-DLTS) was applied to study impurity-induced defects, their density and energy distribution in the energy range of 0.01 eV≤E−Ev≤1.1 eV above the valence band. It was shown, that differential capacitance–voltage, and Hall effect measurements combined with DLTS data can be used to determine the degree of compensation, and the concentration of compensating donors (mostly the positively charged single-substitutional nitrogen (N+)) in p-type CVD polycrystalline diamond films. It was found, that incorporated boron atoms induce three levels of electrically active defects. Two of them with concentration (2–3)×1016 cm−3 each have activation energies of 0.36 and 0.25 eV with capture cross-sections of 1.3×10−13 and 4.5×10−19 cm2, respectively. The third type of defect has an activation energy of 0.02 eV, capture cross-section 3×10−20 cm2 and concentration 1015 cm−3, this shallow trap being a probable general caterer of holes in low-doped films. The total concentration of electrically active uncompensated acceptors in all p-type diamond samples was approximately 2×1017 cm−3 with hole concentration of approximately 1.5×1014 cm−3 and hole mobility in the range of 30–40 cm2 V−1 s−1 at room temperature. If assumed that compensating donors are mostly nitrogen, the films contained no less than 3×1016 cm−3 of N+.

The parameters of trapping centers in CVD diamond films before and after post deposition treatment surface by hydrogen and argon plasma and in diamond p-n junction were studied for the first time by new isothermal Charge-based Deep Level Transient Spectroscopy (Q-DLTS). The concentrations, activation energies, capture cross-sections and locations of the trapping centers were determined. The Q-DLTS showed that micro defects of the all samples with CVD diamond films and in diamond pn junction are acting as trapping centers (point defects) and have the continuous energy spectrum with one or two maximums at different energies.It was found that as-deposited diamond surface were characterized by the high density of the surface point defects - electrical active trapping centers. A treatment of diamond surface with hydrogen plasma substantially decreased a density of defects. Zn the case of argon treated, the Ar plasma induced new point defects and changed their energy distribution.Deep levels with energies E-A approximate to 0.4 eV, E-D approximate to 0.8 eV and related capture cross-sections sigma(A) approximate to 10(-14) cm(2), sigma(D) approximate to 10(-14) cm(2) were obtained from Q-DLTS spectra of diamond p-n junction. Analysis of the Q-DLTS spectra measuring at different conditions was shown that parameters E-A, sigma(A) characterize point defects induced by boron in p-type CVD diamond film, and E-D, sigma(D)- induced by arsenic in n-type synthetic diamond crystal.

Nitrogen doping of thin nanocrystalline diamond films (1-0.2 pm thick) was studied with a particular aim to study an influence of the nitrogen incorporation on the electrical and photoelectrical properties of the structures metal/diamond film/substrate. The diamond films were deposited on n Si substrate from CH4-H-2-N-2 gas mixtures by a de plasma CVD. The best structures with nitrogen-doped nanocrystalline diamond film had low dark conductivity and low density of trapping centers. These structures showed a sharp cut-off in the photoresponse at 220 nm and high quantum yield which depend on nitrogen concentration in diamond film. A broad band around 250-500 nm was observed and attributed to optical excitation of point defects or nitrogen-vacancy clusters (N3 centers). Was shown that the prepared structures can be used as photodiode UV-vis detectors or as W-vis photovoltaic cells with the photovoltage in open-circuit regime of about 0.3 V and high quantum yield of about 0.4 at 200 nm.The experimental results were analyzed and used for design of energy band diagram of metal/diamond film/n-Si structure.

Optical techniques and devices for controlling the parameters of semiconductor structures and manufacturing processes are developed. Novel multi-purpose optical-polarization elements are created, and, on their basis, various precision automatic reflectometers, ellipsometers, and reflection-differential spectrometers are designed and manufactured.

Band bending formation on thin nanocrystalline diamond films and field electron emission after post-growth treatments was investigated. It was found that treatment of the diamond surface with hydrogen plasma substantially decreases the density of point defects, forms the downward band bending and enhances the field electron emission from the films. In the case of an argon plasma treated diamond surface, new point defects were induced and their energy distribution was changed. Nevertheless, the downward band bending was formed and the field electron emission was enhanced similar to the H–plasma-treated diamond surface with minor density of defects. These effects were interpreted in terms of the electrical dipole formation on the plasma treated diamond surfaces. Coating the diamond films with ultrathin metal (Ni, Ti) layers revealed the dependence of the band bending and field emission behavior on the type and thickness of the metal used. The deposition of a few monolayers of Ni on the diamond surface was found to raise the position of the Fermi level relative to the valence band maximum and cause the downward band bending, reducing the field emission threshold. It was suggested that the charge of the surface dipoles on the metal coated diamond surfaces (as in the case of the H and Ar plasma treatments) plays a key role in the band bending formation.

The electrical characteristics of multilayer structures based on amorphous ultrathin diamondlike carbon films were investigated including dynamic and quasi-static current-voltage characteristics, capacitance-voltage characteristics, deep level transient spectra. The effect of illumination and temperature on these characteristics was also investigated. For the multilayer structures composed of lower band gap amorphous carbon layers separated with higher band gap ones, there were observed well-defined regions of negative differential resistance and sharp 20-fold changes in capacitance at definite voltages. Activation energies, capture cross sections, and locations of trapping centers were defined. The effects observed are discussed in terms of trap-assisted tunneling and, also, in terms of resonant tunneling between energy levels in superlattices and charge filling of the quantum wells and trapping centers.

Results are reported on characterization of the field electron emission from diamond films grown by dc arc discharge plasma CVD onto Si substrates from CH 4 -H 2 gas mixtures. The field electron emission was observed at 15-20 V/μm. Emission current-voltage dependences were studied for films prepared at different CVD conditions and post-growth surface treatment/ modification (ultrathin metal and metal oxide coatings, MW-plasma processing, laser-induced surface graphitization). Features of emission current versus applied field behaviour (including a hysteresis phenomenon, vacuum arc initiation) and ultralow (0.1-0.5 eV) values of effective work function derived from Fowler-Nordheim plot fitting are discussed. A high vacuum scanning tunneling-field emission microscope was applied for simultaneous mapping of field electron emission intern-sity. topography and work function to study electronic and structural properties of field emission centers.

Diamond-like carbon (DLC) films with 4-400 nm thickness were deposited on silicon substrates using direct ion beam from an RF inductively coupled CH4 - plasma (ICP) source. The dependence of the film electrical and photoelectrical properties on methane flow were examined. Two kinds of trapping centers with different activation energies and capture cross-sections, and very low densities were discovered by the Q-DLTS method. The influence of thermal annealing in air at 100-450°C was investigated. The current leakage and defect concentration were reduced while electrical breakdown field and photoresponse were increased in annealed films. The results obtained have been used for optimization of the technology to prepare thin films with good protective, electrically insulating, and passivating properties.

The parameters of trapping centers in CVD diamond and Diamond-Like Carbon (DLC) films were studied by Charge Deep Level Transient Spectroscopy (Q-DLTS). The concentrations, activation energies, captures cross-section and location of the trapping centers were determined. The influence of post deposition heat treatment on the defect center parameters was studied. The Q-DLTS measurements showed that micro defects are acting as point trapping centers and have the continuous energy spectrum with one or two maximums at different energies. The nature of the trapping centers is discussed.