D. Sueva

• PhD
• Professor (Associate) at Sofia University "St. Kliment Ohridski"

A course in Classical Mechanics for undergraduate university students studying Physics as a primary subject. The textbook is intended to develop an understanding of theoretical concepts and laws by experimenting. It provides also an introduction to the basic principles and rules of Experimental Physics in order to serve as preparation for further s...

The influence of rapid thermal annealing (RTA) on the properties of a-C: H/c-Si (p-type) structures was investigated. The carbon layers were deposited by plasma enhanced CVD at substrate temperature of 340°C from methanol (CH3OH) vapor. The C-V and I-V measurements of the a-C: H/Si structures showed that a p-n junction is formed on the silicon surf...

The measurement system is designed to have a Si n+–p–p+ detector and current amplifier. It is examined in strong gamma fields. The detector works in a current-generation mode without applying reverse voltage. The amplifier measures currents in the range of 10−6–10−12A. The output current is proportional to the gamma-ray intensity. By integrating th...

We investigated the SiC interface layer formation by the rapid thermal annealing (RTA) of a-C:H/c-Si (p-type) structures at 800, 1000 and 1200°C for 3 minutes. The a-C:H layers, about 120 nm thick, were deposited by HF PECVD from methanol at a substrate temperature of 340°C. The creation of a SiC interface layer was established by Raman spectroscop...

The change in the contact potential difference (CPD) due to ethanol vapor adsorption by a-Si:H/c-Si structure is measured by Kelvin’s method. The measurements are carried out in dry nitrogen ambient and temperature in the interval 20–100°C. Two types of electrically active adsorption are established—reversible and nonreversible. The reversible etha...

The carrier transport in ITO/a-Si:H/Pd position sensitive detector is studied experimentally and numerically. Hydrogenated amorphous silicon deposited by the homogeneous chemical vapour deposition process (HOMOCVD) is used as an active layer. A method which allows estimation of the a-Si:H electron trap density (Nt) and the effective electron diffus...

Two types of silicon detectors are reported (ion implantation and surface barrier detector) for the detection of neutrons in high gamma-background. The purpose is to find an optimal design of silicon detector combined with the neutron converter, which is efficient enough to neutron flux and with low sensitivity to gamma-rays. The experiments show t...

Neutron detectors based on ITO/p-Si structure are fabricated and investigated. The ITO layer is deposited on p-type (100)Si with resistivity 60Ωcm by DC reactive magnetron sputtering of a 90%In–10%Sn target at 450°C substrate temperature. The low temperature of the deposition process retains the large lifetime of the minority carriers in the Si waf...

The electrical and photoelectrical characteristics of the a-Si:H/c-Si (p-type) structure are measured. The structure is analysed as a Schottky diode in which the a-Si:H is considered as a diffusion barrier layer. The conventional h.f. C–V theory is simplified and adapted to the analysis, which allows to estimate the initial band bending at the c-Si...

Position-sensitive photodetectors (PSD) on the basis of a p-cSi/a-Si:H structure have been developed. Thin undoped hydrogenated amorphous silicon films were deposited by the homogeneous chemical vapour deposition (Homogeneous CVD) method on a p-type crystalline silicon (c-Si) substrate of 10 Ω cm resistivity. Strip parallel lateral aluminium positi...

One- and two-dimensional position sensitive detectors based on an ITO - pSi structure have been fabricated and studied. The experimentally measured linear dependence between the photovoltage response and the light spot position is explained by a model in which the electric field in silicon in the lateral direction is assumed to be constant. It has...

Deep level transient spectroscopy (DLTS), C–V and I–V measurements were carried out on silicon n+–p–p+ neutron detectors using the reaction 6Li(n,α)3H. The samples were investigated before and after irradiation with nuclear power reactor neutrons with fluence 1.0×1014n/cm2. DLTS spectra of detectors wrapped in a cadmium foil during irradiation show...

A physical model is presented which allows calculation of the carrier and potential distributions and the output voltage of a one dimensional position sensitive detector based on an ITO/a-Si:H/Pd structure. The calculation results are in agreement with those experimentally measured. Using the experimental data the effective electron diffusion lengt...

-p-π-p+ silicon avalanche diodes for the detection of heavy charged particles. Two sets of measurements of the alpha spectrum of 241Am were carried out, one without acollimator and one with acollimator. The obtained alpha spectra for all bias voltages differ substantially from the spectrum obtained with aconventional semiconductor detector. The exp...

Deep level transient spectroscopy (DLTS) and lifetime measurements were carried out on silicon p+nn+ diodes before and after irradiation with fast neutrons at room temperature with fluences of 5.5 × 1011 and 1.0 × 1012 n/cm2. In the non-irradiated samples the observed levels satisfactorily explained the measured data of recombination and generation...

The design, fabrication and characterization of hydrogenated amorphous silicon (α-Si:H) position sensitive photodetectors (PSP) are described. Thin undoped α-Si:H films were deposited by homogeneous chemical vapour deposition using thermal decomposition of silane at low gas pressure. The thin films were characterized by their dark and photoconducti...

Deep-Level Transient Spectroscopy (DLTS) measurements were carried out on silicon p(+)nn(+) diodes before and after irradiation with fast neutrons at room temperature with fluences 5.5 x 10(11) and 1.0 x 10(12) n/cm(2). It was found out, that all preexisting defects decreased their amplitudes during irradiation, while only one defect, identified as...

The performance of n- and p-type silicon detectors manufactured by a recently developed planar technology for the detection of β-particles, conversion electrons and γ-rays is reported. Two structures are tested: an ion implanted detector with p+-n-n+ structure and a diffusion detector with n+-p-p+ structure.The experiments show that planar detector...

Two types of detectors were developed by conventional planar technology: a p⁺-n-n⁺ ion-implanted detector and a n⁺p-p⁺ diffused detector. There was no observable difference in the quality of the detectors manufactured in this way. Both detectors were investigated for alpha and beta spectroscopy and exhibi...

The note demonstrates the potential capabilities for X-ray analysis by avalanche detectors with relatively thick drift regions. The experiments showed that Si AD can be used in X-ray analysis of the K lines of all elements from the first half of the Periodic Table and of the L and M lines of almost all elements. The standard planar technology used...

Three types of silicon avalanche detectors for low energy gamma- and X-ray counting were manufactured using planar and planar-epitaxial technology. The detectors were tested at room temperature with 57Co and 241Am. Besides the characteristic lines of the sources additional peaks were observed due to X-rays of elements included in the matrices and h...

Silicon detectors for alpha, gamma, neutron and fission fragment radiation spectrometry have been prepared, by applying low energy (3 and 5 keV) ion implantation techniques together with appropriate mechanical and chemical treatment. The spectrometric measurements were carried out at room temperature. The radiation stability of the detectors was ch...

The low-energy ion implantation method of boron and phosphorus in p- and n-type silicon is used in conjunction with appropriate methods for mechanical and chemical surface treatments of the materials to fabricate semiconducting detectors for alpha-particle spectrometers. High-quality p-n junctions with low reverse currents were obtained. With a 30-...