Browsing by Author "Evtodiev, I."

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CARACTERISTICI NUMERICE ŞI LEGITĂŢI STATISTICE ÎN TEORIA FIABILITĂŢII
(Universitatea de Stat „Alecu Russo“ din Bălţi, 2015) Evtodiev, S.; Veleșcu, D.; Evtodiev, I.
Articolul dat se referă la caracteristicile numerice ale fiabilităţii şi repartiţia funcţiilor de fiabilitate după legităţile statistice din teoria fiabilităţii. Am studiat mai în detaliu Legea Gamma şi Legea Weibull cu 1 parametru, 2 parametri şi 3 parametri.
LUMINESCENCE OF β-Ga2O3 NANOFORMS OBTAINED BY OXIDATION OF GaSe DOPED WITH Eu
(Springer, Cham, 2020) Sprincean, Veaceslav; Untila, D.; Chirița, Arcadii; Evtodiev, I.; Caraman, I.
The GaSe single crystals were doped with Eu in the process of their synthesis and growth. The oxide of β-Ga2O3 doped with Eu in the form of massive nanowires was obtained by thermal treatment (TT) in the atmosphere of GaSe single crystals doped with 1.0 and 3.0 at.% of Eu. The crystalline structure, surface morphology and photoluminescence spectra of GaSe:Eu and β-Ga2O3:Eu single crystals were studied. The Photoluminescence (FL) spectrum of GaSe doped with 1.0 at.% of Eu at room temperature is formed as a result of transitions of 5D0 →7F1 to Eu3+ ion and as a result of radiation annihilation of n = 1 excitons in GaSe. The FL spectra of Ga2O3:Eu was interpreted on the basis of the energy level diagram of electrons in Eu3+ ion.
OPTICAL AND PHOTOELECTRICAL CHARACTERISTICS OF GaSe (Cu)/OXIDE SEMICONDUCTOR HETEROJUNCTION
(2008) Evtodiev, I.; Cuculescu, E.; Arama, E.; Caraman, M.
The AIIIBVI layered semiconductors are perspective materials for photoelectrical and luminescent device fabrication, for use in visible and near IR spectral region [1, 2]. GaSe and InSe semiconductors, having the bandgap equal to 2.0 eV and 1.2 eV respectively, are most often used for device fabrication [3, 4]. The applicability of GaSe crystals as a heterojunction component is limited by their low electrical conductivity (the hole concentration is ∼ 1013 cm-3 at 293 K) [5]. Cu (0.10 at %) doping of GaSe crystals causes the hole conductivity increase by more than 5 orders of magnitude and its value is ∼ (8÷9)⋅10-2Ω-1cm-1 [6]. Cu impurity atoms form two acceptor levels in GaSe positioned at 0.12 eV and 0.038 eV [1], which enlarge the applicability domain for these materials. The SnO2, In2O3 (SnO2), ZnO and others [7, 8] are used as optically transparent semiconductors in the visible and near IR spectral region and as an element of heterojunction based optoelectronic devices. This paper presents the investigation of the photoelectrical properties of GaSe (0.10 at % Cu)/ ZnO, In2O3, SnO2, Bi2O3, and Cu2O oxide semiconductor heterojunction.
OPTICAL PROPERTIES OF COMPOUNDS WITH SUBMICRON POINTS OBTAINED THROUGH Ga2S3 INTERCALATION WITH Cd
(Universitatea de Stat „Alecu Russo“ din Bălţi, 2012) Racoveț, O.; Evtodiev, I.; Caraman, Iu.; Rotaru, I.; Lazăr, G.
Luminescence and optical absorption spectra of Ga2S3 single crystals were investigated at temperatures of 78 K and 293 K. Optical band gap is equal to 3.27 eV and 3.457 eV at 293 K and 78 K respectively. Luminescence spectrum of single crystal lamellas at temperature of 78K consists of three bands with peaks at 2.04 eV, 1.84 eV and 1.66 eV.Native structural defects form deep recombination and electronic capture levels localized within the Ga2S3 band gap.
Optical Properties of III–VI Lamellar Semiconductors Doped with Cu and Cd and of Related III–VI/Native Oxide Structures
(American Scientific Publishers, 2011) Evtodiev, Silvia; Caraman, Iulia; Dmitroglo, Liliana; Leontie, L.; Nedeff, V.; Dafinei, A.; Lazar, G.; Evtodiev, I.
GaS, GaSe and GaTe are typical representatives of III–VI layered semiconductor materials, showing highly anisotropic mechanical and optical properties. At photon energies hν < E g , the anisotropy ratio for the absorption coefficients at the n = 1 excitonic peak, corresponding to E →‖C → and E →⊥C → polarizations, is α ‖/α ⊥≈15. Optical functions n e (λ) and n o (λ) of GaS and GaSe in the wavelength range 0.36–22 μm have been determined. For the photon energies hν < E g ind, these correspond to a normal dispersion and can be described by power-law wavelength dependences. By means of FTIR transmission and reflection spectroscopy in the spectral range of 1000–85 cm−1, for plan-parallel plates with thickness between several tens of nanometers and centimeters, the wavenumbers of longitudinal optical ν(LO) and transverse optical ν(TO) phonons have been determined for GaSe [ν ⊥(LO) = 254 cm−1, ν ⊥(TO) = 214 cm−1], GaS [ν ⊥(LO) = 359 cm−1, ν ⊥(TO) = 297 cm−1, ν ‖(LO) = 336 cm−1], and GaTe [ν(LO) = 164 cm−1, ν(TO) = 118 cm−1].
SOLUBILITATEA METALELOR DE Fe ÎN CRISTALELE GaSb
(Universitatea de Stat „Alecu Russo“ din Bălţi, 2012) Georghită, E.; Mihălache, A.; Evtodiev, I.
În baza spectrelor de energie atomică s-a studiat distribuţia atomilor de Fe în volumul materialului de puritate înaltă GaSb crescut prin metoda topirii zonale şi dopat cu Fe.