• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.51 no.3
• /
• pp.137-141
• /
• 2002

CdS and $CdS:Co^{2+}$ single crystals were grown by CTR method using iodine as transport material. The grown single crystals have defect chalcopyrite structure with direct band gap. The optical energy band gap was decreased according to add of Co-impurity. We can observed the Co-impurity optical absorption peaks assigned to the $Co^{2+}$ ion sited at the $T_d$ symmetry lattice and we consider that they were attributed to the electron transitions between energy levels of ions.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.25 no.4
• /
• pp.402-406
• /
• 1988

The MgGa2Se4 single crystal for study of optical properties is for the first time grown by Bridgmna method. The crystal structure of grown MgGa2Se4 single crystal has the Rhomobohedral structure (R3m) and its lattice constant are a=3.950\ulcorner c=38.893\ulcornerin Hexagonal structure. The energy band structure of grown MgGa2Se4 single crystal structure has direct band gap and the optical energy gap measured from optical absorption in this crystal is 2.20eV at 290K. The temperature dependence of energy gap was given Eg(T)=Eg(O)-aT\ulcorner)B+T), from varshni equation, where Eg(O)=2.34eV, a=8.79x10**-4eV/and b=250K.

• Journal of the Korean Vacuum Society
• /
• v.4 no.3
• /
• pp.334-341
• /
• 1995

IB-AI-VIB2 및 IB-AI-VIB2 :Co2+ 결정을 고순도 원소를 출발 물질로 하고 iodine을 수송 매체로 사용하여 chemical transport reaction method로 성장시켰다. 성장된 결정의 결정구조는 chalcopyrite 구조였으며, energy gap은 direct band gap으로 3.514~1.814 eV 정도로 주어졌으며, cobalt를 불순물로 첨가할 때 energy gap은 감소하였다. IB-AI-VIB2 :Co2+ 결정에서 첨가된 cobalt가 모체결정의 Td symmetry site에 Co2+ ion으로 위치하여, Co2+ ion의 energy 준위 사이의 전자전이에 기인하는 불순물 광흡수 peaks가 나타났다. 이 불순물 광흡수 peaks에 결정장 이론을 적용하여 구산 1st-order spin-orbit coupling parameter(λ)는 -183~ -189cm-1정도였고, 2nd-order spin-orbit coupling parameter(P)는 225~239 cm-1정도였으며, crystal field parameter(Dq)는 328~395cm-1, Racah parameter(B)는 531~552cm-1정도였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11b
• /
• pp.1-6
• /
• 2004

In this paper author describe the undoped and $Co^{2+}$ (0.5mole%)doped $Cd_4GeS_6$ single crystals were grown by the chemical transporting reaction(CTR) method using high purity(6N) Cd, $GeS_2$, S elements. It was found from the analysis of X-ray diffraction that the undoped and $Co^{2+}$(0.5mole%) doped $Cd_{4}GeS_{6}$ compounds have a monoclinic structure in space grop Cc. The optical energy band gap was direct band gap and temperature dependence of optical energy gap was fitted well to Varshni equation. Impurity optical absorption peaks due to the doped cobalt in the $Cd_4GeS_6:Co^{2+}$ single crystal were observed at 3593cm-1, 5048cm-1, 5901cm-1, 7322cm-1, 12834cm-1, 13250cm-1, 14250cm-1，and 14975cm-1 at 11.3K.

• Transactions on Electrical and Electronic Materials
• /
• v.6 no.5
• /
• pp.229-232
• /
• 2005

Direct characterization of band alignment at chemical bath deposition $(CBD)-CdS/Cu_{0.93}(In_{1-x}Ga_x)Se_2$ has been carried out by photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). Ar ion beam etching at the condition of the low ion kinetic energy of 400 eV yields a removal of surface contamination as well as successful development of intrinsic feature of each layer and the interfaces. Especially interior regions of the wide gap CIGS layers with a band gap of $1.4\~1.6\;eV$ were successfully exposed. IPES spectra revealed that conduction band offset (CBO) at the interface region over the wide gap CIGS of x = 0.60 and 0.75 was negative, where the conduction band minimum of CdS was lower than that of CIGS. It was also observed that an energy spacing between conduction band minimum (CBM) of CdS layer and valance band maximum (VBM) of $Cu_{0.93}(In_{0.25}Ga_{0.75})Se_2$ layer at interface region was no wider than that of the interface over the $Cu_{0.93}(In_{0.60}Ga_{0.40})Se_2$ layer.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.7
• /
• pp.304-307
• /
• 2005

The $In_2S_3\;and\;In_2S_3:Co^{2+}$ thin films were grown by the spray Pyrolysis method. The thin films crystallized into tetragonal structures. The indirect energy band gap was 2.32ev for $In_2S_3\;and\;1.81eV\;for\;In_2S_3:Co^{2+}$ at 298K. The direct energy band gap was 2.67ev for $In_2S_3:Co^{2+}$ thin films. Impurity optical absorption peaks were observed for the $In_2S_3:Co^{2+}$ thin films. These impurity absorption peaks are assigned, based on the crystal field theory to the electron transitions between the energy levels of the $Co^{2+}$ ion sited in $T_{d}$ symmetry. The electrical conductivity($\sigma$), Hall mobility(${\mu}_H$), and carrier concentration (n) of the $In_2Se_3$ thin film were measured, and their temperature dependence was investigated.

• Korean Journal of Materials Research
• /
• v.15 no.3
• /
• pp.195-201
• /
• 2005

The $SnS_2,\;SnS_2:Cd$, and $SnS_2:Sb$ single crystals were grown by the chemical transport reaction method. The indirect optical energy band gap was found to be 2.348, 2.345, and 2.343 eV for the $SnS_2,\;SnS_2:Cd$, and $SnS_2:Sb$ single crystals, at 6 K respectively. The direct optical energy band gap was found to be 2.511, 2.505, and 2.503 eV f3r the $SnS_2,\;SnS_2:Cd$, and $SnS_2:Sb$ single crystals, at 6 K respectively The temperature dependence of the optical energy band gap was well fitted by the Varshni equation. Two photoluminescence emission peaks with the peak energy of 2.214 and 1.792 eV for $SnS_2$, 2.214 and 1.837 eV for $SnS_2:Cd$, and 2.214 and 1.818 eV the $SnS_2:Sb$ were observed. The emission peaks were described as originating from the donor-acceptor pair recombinations.

• Electrical & Electronic Materials
• /
• v.10 no.2
• /
• pp.105-112
• /
• 1997

Undoped and Co$^{2+}$-doped Zn$_{4}$GeSe$_{6}$ single crystals were grown by the Chemical Transport Reaction method using iodine as a transporting agent. The crystal structure of these compounds determined by X-ray diffraction analysis was monoclinic structure. The direct energy gaps of these compounds were measured and the temperature dependence of the optical energy gap were closely investigated over the temperature range 10-290K. The temperature dependence of the optical energy gap is well presented by the Varshni equation. Also the optical absorption peaks of Zn$_{4}$GeSe$_{6}$ :Co$^{2+}$ single crystal observed, centered at 5437, 6079, 7142, 12950, 13462, 14786 and 15735 $cm^{-1}$ /, can be explained in terms of the electronic transitions of Co$^{2+}$ ions located at Td symmetry of the host materials. According to the crystal-field theory, the crystal-field, Racah and spin-orbit coupling parameters obtained from the absorption bands are given by Dq = 361$cm^{-1}$ /, B = 655$cm^{-1}$ / and .lambda. = 284$cm^{-1}$ / respectively.ively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.305.2-305.2
• /
• 2016

Tin monosulfide (SnS) is one promising candidate absorber material which replace the current technology based on cadmium telluride (CdTe) and copper indium gallium sulfide selenide (CIGS) for its suitable optical band gap, high absorption coefficient, earth-abundant, non-toxic and cost-effective. During past years work, thin film solar cells based on SnS films had been improved to 4.36% certified efficiency. In this study, Tin monosul fide was obtained by atomic layer deposition (ALD) using the reaction of Tetrakis (dimethylamino) tin (TDMASn, [(CH3)2N]4Sn) and hydrogen sulfide (H2S) at low temperatures (100 to 200 oC). The direct optical band gap and strong optical absorption of SnS films were observed throughout the Ultraviolet visible spectroscopy (UV VIS), and the properties of SnS films were analyzed by sanning Electron Microscope (SEM) and X-Ray Diffraction (XRD).

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.41 no.9
• /
• pp.1085-1094
• /
• 1992

A variable-spacing cesium thermionic energy conversion test station is designed and fabricated for the study of power generation. The diode is in the form of a guard-ringed plane-parallel geometry in which a polycrystalline rhenium emitter of 2 cmS02T area faces a radiation-cooled polycrystalline rhenium collector of 1.9 cmS02T area. The emission of plasma from heated refractory electrode metal is the driving reaction in the direct conversion of heat to electricity by thermionic energy conversion. The plasma is produced from electrons and positive ions formed simultaneously by thermionic emission and surface ionization of cesium atoms incident on the hot emitter from the cesium vapor in the diode. And high plasma density causes plasma multiplication within the gap due to volume ionization that results in high power output. The variation of the saturation current of a Knudsen converter is investigated at an emitter-collector gap of 0.1 mm and an emitter temperatures. A maximum power output of 13.47 watta/cmS02T is observed at a collector temperature of 963 K and a cesium reservoir temperature of 603 K.