Aluminum nitride films have been synthesized by reactive magnetron sputtering on n-Si(100) substrates. AlN layers with thicknesses from 2 to 150 nm were obtained to establish a correlation between the structure of the films and their electrical conductivity. Electron microscopy revealed that the amorphous structure of the films passes to nanocrystalline one while moving away from the substrate surface. Films with thicknesses below 20 nm had a high conductivity: up to 10 (Ω cm)–1; with an increase in thickness the conductivity dropped to 10–7 (Ω cm)–1. The high conductivity of thin AlN layers is believed to be due to the high density of the boundaries of grains built-in into amorphous matrix.

Пленки нитрида алюминия синтезированы с помощью метода реактивного магнетронного напыления на кремниевых подложках n-Si (100). Слои AlN толщиной от 2 до 150 нм получены с целью установления корреляции между строением пленок и их электропроводностью. С помощью электронной микроскопии установлено, что по мере удаления от поверхности подложки аморфное строение пленки переходило к нанокристаллическому. Пленки с толщинами до 20 нм имели высокую проводимость до 10 (Ом·см)–1, при увеличении толщины проводимость резко падала до 10–7 (Ом·см)–1. Предполагается, что высокая проводимость тонких слоев AlN обусловлена высокой плотностью границ зерен, встроенных в аморфную матрицу.

В статье демонстрируется работа модели компактного калибровочного источника нейтронов, который может быть использован для калибровки и определения функции отклика детекторов темной материи и детекторов электронных антинейтрино. Рассматриваемый калибровочный источник нейтронов представляет собой комбинацию радионуклида \({}^{252}\) Cf, который испытывает спонтанное деление с образованием нейтронов, и оригинального кремниевого полупроводникового детектора. Последний обеспечивает временную привязку к моменту образования нейтронов путем регистрации сигналов от осколков деления.

Influence of the prolonged irradiation by fission products of 252Cf radionuclide on the operational parameters of silicon-lithium Si(Li) p-i-n detectors, Si surface barrier detectors and Si planar p+n detector was investigated. The obtained results revealed a linear shift of the fission fragment peaks positions towards the lower energies with increase of the irradiation dose for all investigated detectors. The rate of the peaks shift was found to depend strongly on the detector type and the strength of the electric field in the detectors active region, but not on the temperature of irradiation (room or liquid nitrogen temperature). Based on the obtained results, the possibility of integration of the investigated types of Si semiconductor detectors in a radionuclide neutron calibration source is considered.

Operation of a model of a compact neutron source that can be used to calibrate dark-matter and electron-antineutrino detectors and to determine their response functions is demonstrated. The calibration neutron source in question is a combination of the ^252 Cf radionuclide, which undergoes spontaneous fission, producing neutrons, and an original silicon semiconductor detector. The latter provides a time reference for the neutron-emission instant by recording signals from fission fragments.

We present a description of the originally developed ������-spectrometer consisting of two Si(Li)-detectors with sensitive area thickness above 8 mm and 4 ������-geometry. The full absorption spectrometer allows for direct measurements of ������-spectra, disregarding the corrections to response function induced by the electron backscattering from the crystal surface. In case of ������-spectra of transitions to the excited state of the daughter isotope additional 3 & DPRIME;BGO-detector is used in order to detect the ������-quanta in coincidence with the pair of Si(Li)-spectrometers.

Deterioration of the operation parameters of Al/SiO2/p-type Si surface barrier detector upon irradiation with alpha-particles at room temperature was investigated. As a result of 40-days irradiation with a total fluence of 8*10^9 α-particles, an increase of α-peak FWHM from 70 keV to 100 keV was observed and explained by increase of the detector reverse current due to formation of a high concentration of near mid-gap defect levels. Performed CV measurements revealed the appearance of at least 6*10^12 cm-3 radiation-induced acceptors at the depths where according to the TRIM simulations the highest concentration of vacancy-interstitial pairs was created by the incoming α-particles. The studies carried out by current-DLTS technique allowed to associate the observed increase of the acceptor concentration with the near mid-gap acceptor level at EV+0.56 eV. This level can be apparently associated with V2O defects recognized previously to be responsible for the space charge sign inversion in the irradiated n-type Si detectors.

Deterioration of the operation parameters of p-type Si surface-barrier detector and Si(Li) p-i-n detector upon irradiation by alpha-particles was investigated. The detectors were irradiated at room temperature up to a total number of the registered α-particles N α equal to 6 × 10 9 . Prolonged irradiation has resulted in a deterioration of the detectors energy resolution ability and it was found that the increase of α-peaks broadening can be described by a linear function of N α with a slope Δσ/Δ N α ∼ (1.4–1.8) × 10 –9 keV/α for both detectors. Resolution deterioration was associated with the increase of the detectors leakage current, which proceeds linearly with the number of absorbed α-particles with the slope ΔI/Δ Nα ∼ (7-17) × 10 -17 A/α. The increase of the detectors reverse current was related with appearance of radiation-induced defect level at 0.56 eV above the valence band.

Herein, the investigation of radiation‐induced defects generated in the Al/SiO2/p‐type FZ Si surface barrier detector upon irradiation with α‐particles at room temperature using capacitance−voltage (C−V) and current deep‐level transient spectroscopy (IDLTS) methods is conducted. The carried out C−V measurements indicate the formation of at least 8 × 1012 cm−3 radiation‐induced acceptor traps at the depth fairly close to that where, according to TRIM simulations, the highest concentration of vacancy‐interstitial pairs is created by the incoming α‐particles. The studies conducted by the current DLTS technique allow to relate the observed increase in the acceptor concentration with the near‐midgap level at E V + 0.56 eV. This level can apparently be associated with V2O defects recognized previously to be responsible for the space−charge sign inversion in the irradiated n‐type Si detectors.

Photoelectric properties of MIS tunnel diodes produced on high-resistive p-type silicon wafers with thin aluminium nitride AlN insulator layer and Pd or Al metal gate electrodes were investigated. It was found that synthesized AlN films possess a fixed positive charge, which leads to the creation of near-surface inversion layer in silicon substrate. The ratio of the photocurrent to the dark current K = Iph / Idark (on / off ratio) was found to depend on the gate electrode material, illumination intensity and the applied reverse bias. For studied MIS structures K ratio varied from 10 4 to 10 5 and was two orders of magnitude higher than that for the control MS structure without the insulator layer. High on / off ratio of such MIS structures with AlN tunnelling insulator promotes their application as an effective photodetectors in optoelectronics.

A spectrometer based on a Si(Li) detector has been tested by exposure to α particles with the aim of determining changes in the detector characteristics versus the fluence. As a result of 60-day measurements with a total fluence of 6.2 × 109 α particles, it has been established that the dependence of the deterioration in the energy resolution of α-particle peaks on the fluence is described by a linear function with a slope of Δσ/ΔФ = (8.4 ± 0.4) × 10–10 keV/α. The measured amplitude of the α-particle momentum decreases linearly with increasing fluence with a slope of (–4.8 ± 0.6) × 10–9 keV/α. These effects do not prevent reliable discrimination between the signals from α particles and fission fragments until the fluence reaches a value of 1010 α particles when the Si(Li) detector is a part of a neutron source for detecting fission fragments.

Present work reports the results of activities intended to reach thin Si(Li) detector entrance window on the diffusive lithium layer side. It was established that the new n-contact represented by a heterostructure of unalloyed amorphous n-type silicon a-Si:H allows one to achieve the entrance window thickness 3 = 4 orders of magnitude smaller than the lithium-side entrance window of standard Si(Li) detectors. The films of amorphous silicon were synthesized with MASD (magnetron assisted silane decomposition) method in mixture of SiH4 (25%) and Ar (75%) gases. Lithium layer surface resistivity and silicon target type (n- or p-) affection on electrical properties of Si(Li) detector contact produced were studied. The investigation performed had led to a technology of Si(Li) detector production with thickness of the entrance window on the diffusive lithium layer side below 0.1 mu m.

The characteristics of a beta spectrometer that consists of a total-absorption Si(Li) detector and a drift Si detector are presented. Using this spectrometer, it is possible to efficiently separate β radiation of nuclei from concomitant X and γ rays. The method is based on coincidences between signals from the thick and thin detectors. The spectrometer can be used to precisely measure the shape of the β spectra of various radioactive nuclei, in particular, of the 144Pr nucleus, which is the most promising antineutrino source for searching for neutrino oscillations into a sterile state.

Here we present the specifications of a newly developed beta-spectrometer, based on full absorption Si(Li) detector and thin transmission detector, allowing one to perform efficient separation beta-radiation and accompanying X-rays and gamma radiation. Our method is based on registration of coincident events from both detectors. The spectrometer can be used for precision measurements of various beta-spectra, namely for the beta-spectrum shape study of Pr-144, which is considered to be an advantageous anti-neutrino source for sterile neutrino searches.

AlN films of different thicknesses were deposited on n-Si (100) substrates by reactive radio frequency (rf) magnetron sputtering. Dependences of structure and electrical properties on thickness of deposited films were researched. The structures of the films were analyzed with scanning electron microscopy (SEM) and with transmitting electron microscopy (TEM). Electrical properties of the films were investigated on Au-AlN-(n-Si) structures by means of current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) techniques. Electron microscopy investigations had shown that structure and chemical composition of the films were thickness stratified. Near silicon surface layer was amorphous aluminum oxide one contained traps of positive charges with concentration of about 4 x 10(18) cm(-3). Upper layers were nanocrystalline ones consisted of both wurzite AlN and cubic AlON nanocrystals. They contained traps both positive and negative charges which were situated within 30 nm distance from silicon surface. Surface densities of these traps were about 10(12) cm(-2). Electron traps with activation energies of (0.2 +/- 0.4) eV and densities of about 10(10) cm(-2) were revealed on interface between aluminum oxide layer and silicon substrate. Their densities varied weakly with the film thickness.

Light-induced fixation of DNA molecules on silicon surface was done and electro-physical properties of Schottky diodes with DNA on interfaces were investigated. Thymus DNA molecules were deposited on silicon from a water solution. Fixed molecular structures were observed with helium ionic microscopy and atomic force microscopy and then they were covered with thermal sputtered gold film. Obtained structures Au–DNA–(n-Si) were examined with current–voltage and frequency dependent admittance measurements. In darkness immobilizing of molecules leaded to form DNA ropes with thickness up to 10nm and distances between them about 1mkm. Fixation under illumination resulted in forming of single DNA mesh with thickness about 1nm and cell size about 100nm. Presence of molecular mesh on interface leaded to increasing of charge density controlled by metal Fermi level and improved diode quality. Presence of molecular ropes resulted in increasing of charge density controlled by semiconductor. From the estimation of interface state density values the origin of the states at the interface between DNA and silicon substrate is suggested to be DNA phosphate groups contacting or being close to the substrate surface.

DNA molecules immobilization on n-type single silicon was investigated. Electronic states were studied by measuring voltage-ampere characteristics (VAC) of Au-(n-Si) contacts with DNA molecules on the interface. It is showed that strong DNA fixation is observed in the presence of magnesium ions in solution. Molecules conformation on the surface is determined by the degree of the substrate hydrophobicity. Developed method of DNA immobilization allows to create model systems with the molecules in the form of molecular mesh or ropes depending on irradiation intensity. Formed on the silicon surface molecular structures have different effect on the electrical properties of Au-DNA-(n-Si) contacts. Presence of molecular mesh on the Schottky diode interface makes its VAC similar to ideal diode. The ropes lead to electronic state density increasing.