비정질 Sb-Bi-Te 박막의 전기적 특성에 관한 연구

이준신,이재형,D. Mangalaraj 한국전기전자재료학회 2002 전기전자재료학회논문지 Vol.15 No.3

Amorphous $Sb_{2-x}Bi_xTe_3$ (x = 0.0, 0.5 and 1.0) thin films were prepared by vacuum evaporation. The resistivity of 7he films decreases from 1.4{\times}10^{-2}$ to $8.84{\times}10^{-5}\Omega cm$ and the type of conductivity changes from p to n with the increase of the x value of the films. D.C. conduction studies on these films ate performed at various electric fields in the temperature range of 303-403 K. At low electric fields, two types of conduction mechanisms, i.e. the variable range hopping and the phonon assisted hopping are found to be responsible for the conduction, depending upon the temperature. The activation energy decreases from 0.082 to 0.076 eV in the temperature range of 303-363 K and from 0.47-0.456 eV in the second range of 363-403 K, indicating the shift of the Fermi level towards the conduction band edge and hence the change of the conduction from P to n type with the increase of the Bi concentration. Poole-Frankel emission dominates at high fields. The shape of the potential well of the localized centre is deduced and the mean free path of the charge carriers is also calculated.

Bi 농도에 따른 비정질 Sb-Bi-Te 박막의 특성

이재형,이준신,D. Mangalaraj 한국진공학회 2002 Applied Science and Convergence Technology Vol.11 No.1

진공 증착한 $Sb_{2-x}Bi_xTe_3$ 박막은 Bi 농도에 관계없이 비정질 형태로 성장되었고, XPS 분석 결과 증착 물질과 거의 유사한 조성을 가짐을 알 수 있었다. 또한 박막의 광학적, 전기적 특성을 설명하기 위해 여러 미세구조 파라미터들을 계산하였다. 한편, 박막 내 Bi 농도가 증가함에 따라 전기 비저항은 급격히 감소하였고, 특히 높은 Bi 농도(x=1.0)에서는 전도 특성이 p-type에서 n-type으로 변화되었다. 또한 $Sb_{2-x}Bi_xTe_3$ 박막의 굴절 지수 및 광학적 밴드 갭은 Bi 농도에 따라 증가하였다. Thin films of $Sb_{2-x}Bi_xTe_3$ (x = 0.0, 0.5, and 1.0) are grown by vacuum evaporation. XRD analysis shows the amorphous nature of the films, and the composition studies confirm the stoichiometry of the films. Microstructural parameters of the films have been calculated and used to explain the electrical and optical properties of the films. It is observed that the carrier type has changed from p- to n-type at higher concentration (x = 1.0) of Bi. The resistivity of the films decreases rapidly with the increase of Bi concentration. However, the refractive index and optical band gap of the films increase with the Bi concentration.

Effect of calcination on the crystallinity of sputtered TiO₂ thin films as studied by Raman scattering

Karunagaran, B.,Mangalaraj, D.,Kim, Kyunghae,Hong, Byungyou,Roh, Yonghan,Park, Cheon Seok,Yi, Junsin Akademie-Verlag 2005 Crystal research and technology Vol.40 No.3

<P>Titanium dioxide films have been deposited using DC magnetron sputtering technique onto silicon substrates at an ambient temperature and at an oxygen partial pressure of 7 × 10 <SUP>–5</SUP> mbar and sputtering pressure (Ar + O<SUB>2</SUB>) of 1 × 10 <SUP>–3 </SUP>mbar. The deposited films were calcinated at 673 and 773 K. The composition of the films as analyzed using Auger Electron Spectroscopy (AES) revealed the stoichiometry with an O and Ti ratio of 2.08. The influence of post-deposition calcination on the Raman scattering of the films was studied. The existence of Raman active modes A<SUB>1g</SUB>, B<SUB>1g</SUB> and E<SUB>g</SUB> corresponding to the Raman shifts are reported in this paper. The improvement of crystallinity of the TiO<SUB>2</SUB> films as shown by the Raman scattering studies has also been reported. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

Improvement of Commercial Silicon Solar Cells with N+-P-N+ Structure using Halogenic Oxide Passivation

k.Chakrebarty,D.Mangalaraj,김경해,J.H.Park,이준신 한국전기전자재료학회 2003 Transactions on Electrical and Electronic Material Vol.4 No.6

This paper describes the effect of halogenic gettering during oxide passivation of commercial solar cell with the n+-p-n+ structure. In order to study the effect of halogenic gettering on n+-p-n+ structure mono-crystalline silicon solar cell, we performed conventional POCl3 diffusion for emitter formation and oxide passivation in the presence of HCl vapors. The n+-p-n+ structure based silicon solar cells were found to have higher short circuit current and minority carrier lifetime. Their performance was also found to be superior than the conventional n+-p-p+ structure based mono-crystalline silicon solar cell. The cell parameters of the n+-p-p+ and n+-p-n+ structure based cells, passivated by HCl assisted oxidation were measured. . The improvement in Isc was attributed to the effect of the increased diffusion length of minority carriers, which came from the halogenic gettering effect during the growth of passivating oxide. The presence of chlorine caused gettering of the cells by removing the heavy metals, if any. The other advantage of the presence of chlorine was the removal of the diffusion induced (in oxygen environment) stacking faults and line defects from the surfaces of the silicon wafers. All these effects caused the improvement of the minority carrier lifetime, which in-turn helped to improve the quality of the solar cells.

Influence of Bi Concentration on the Electrical and ac Conduction Propertiesof Amorphous Sb-Bi-Te Thin Films

이재형,JunsinYi,D.Mangalaraj 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.1

Amorphous Sb$_{2-x}$Bi$_x$Te$_3$ ($x$=0.0, 0.5 and 1.0) thin films were formed by using vacuum evaporation. In the Hall studies, a p- to n-type conduction change was observed at higher Bi concentrations, and that change was attributed to the unpinning of the Fermi level. The ac conductivity data of the Sb$_{2-x}$Bi$_x$Te$_3$ ($x$=0.0, 0.5 and 1.0) thin films were obtained using a capacitor structure with aluminium as electrodes. The temperature dependence of the ac conductivity was explained on the basis of polaronic-type conduction by comparing the numerical ac conductivity data of bipolarons and single polarons. From the comparison, it was found that the numerical bipolaron conductivity behaved similarly to that of the experimental conductivity whereas the numerical single polaron conductivity differed, thus confirming the bipolaronic nature of conduction in Sb-Bi-Te thin film systems. Higher Bi concentrations were observed to produce more dangling-bond defect states. The ac activation energy values indicated that the conductivity was of an electronic (electrons or holes) hopping type.

Improvement of Commercial Silicon Solar Cells with N⁺-P-N⁺ Structure using Halogenic Oxide Passivation

K. Chakrabarty,D. Mangalaraj,Kim, Kyung-Hae,Park, J.H.,J. Yi The Korean Institute of Electrical and Electronic 2003 Transactions on Electrical and Electronic Material Vol.4 No.6

This paper describes the effect of halogenic gettering during oxide passivation of commercial solar cell with the $N^{+}$-P-$N^{+}$ structure. In order to study the effect of halogenic gettering on $N^{+}$-P-$N^{+}$ structure mono-crystalline silicon solar cell, we performed conventional POCl$_3$ diffusion for emitter formation and oxide passivation in the presence of HCl vapors. The $N^{+}$-P-$N^{+}$ structure based silicon solar cells were found to have higher short circuit current and minority carrier lifetime. Their performance was also found to be superior than the conventional $N^{+}$-P-$N^{+}$ structure based mono-crystalline silicon solar cell. The cell parameters of the $n^{+}$-p-$p^{+}$ and $n^{+}$-p-$n^{+}$ structure based cells, passivated by HCl assisted oxidation were measured. The improvement in $I_{sc}$ was attributed to the effect of the increased diffusion length of minority carriers, which came from the halogenic gettering effect during the growth of passivating oxide. The presence of chlorine caused gettering of the cells by removing the heavy metals, if any. The other advantage of the presence of chlorine was the removal of the diffusion induced (in oxygen environment) stacking faults and line defects from the surfaces of the silicon wafers. All these effects caused the improvement of the minority carrier lifetime, which in-turn helped to improve the quality of the solar cells.

Metal Surface Treatment Effects on Screen Printed Silicon Solar Cells

K.Chakrabarty,D.Mangalaraj,김경해,S.K.Dhungel,J.H.Park,이준신,S.N.Singh 한국전기전자재료학회 2003 Transactions on Electrical and Electronic Material Vol.4 No.4

High series resistance due to the presence of glass frit is one of the major problems for screen printed silicon solar cells. Cells having electrical parameters below the prescribed values are usually rejected during solar module fabrication. Therefore, it is highly desirable to improve the electrical parameters of the silicon solar cells and thereby to increase the overall production yield. It was observed that, the performance of low quality mono-crystalline silicon solar cells made by standard screen printing technology could be improved remarkably by novel surface treatment. We have chemically treated the surface using sodium hydroxide (NaOH) and silver nitrate (AgNO3) solutions. NaOH treatment helps to reduce the series resistance by decreasing the presence of excess glass frit on the top silver grid contact. The AgNO3 treatment is used to reduce the series resistance comes from the deposition of silver on the grids by filling the holes present (if any) within the grid pattern.

Metal Surface Treatment Effects on Screen Printed Silicon Solar Cells

Chakrabarty K.,Mangalaraj D.,Kim K. H.,Dhungel S. K.,Park J. H.,Singh S. N. The Korean Institute of Electrical and Electronic 2003 Transactions on Electrical and Electronic Material Vol.4 No.4

High series resistance due to the presence of glass frit is one of the major problems for screen printed silicon solar cells. Cells having electrical parameters below the prescribed values are usually rejected during solar module fabrication. Therefore, it is highly desirable to improve the electrical parameters of the silicon solar cells and thereby to increase the overall production yield. It was observed that, the performance of low quality mono-crystalline silicon solar cells made by standard screen printing technology could be improved remarkably by novel surface treatment. We have chemically treated the surface using sodium hydroxide (NaOH) and silver nitrate ($AgNO_3$) solutions. NaOH treatment helps to reduce the series resistance by decreasing the presence of excess glass frit on the top silver grid contact. The $AgNO_3$ treatment is used to reduce the series resistance comes from the deposition of silver on the grids by filling the holes present (if any) within the grid pattern.

Argon Implantation E ects on the Structural and the Optical Properties of Vacuum Evaporated CdS Thin Films

JaehyeongLee,JunsinYi,KeajoonYang,D.Mangalaraj 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.5

Vacuum evaporated cadmium sulphide (CdS) thin lms were implanted with Ar+ at dierent doses. The X-ray diffraction (XRD) pattern of the as-deposited film showed a hexagonal structure with a preferred orientation along the (002) plane. Formation of Cd metallic clusters was observed in ion-implanted lms from the XRD patterns. The band gap of the Ar+-implanted lms decreased from 2.385 eV for the as-deposited lm to 2.28 eV for maximum implantation whereas the absorption coecient increased with increasing implantation dose. Raman scattering due to the Al(LO) phonon was observed at 299 cm

Influence of Nitrogen Implantation on the Structural and Optical Properties of CdS Thin Films

이재형,DonggunLim,JunsinYi,KeajoonYang,D.Mangalaraj 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.5

The effects of nitrogen-ion implantation on vacuum-evaporated cadmium sulphide (CdS) thin films were investigated using X-ray diffraction (XRD), optical transmittance spectra, and Raman scattering studies. X-ray diffraction studies revealed that the as-deposited CdS films had a hexagonal structure with a preferential (002) orientation. The XRD patterns revealed formation of Cd metallic clusters in the ion-implanted films. The band gap of the N$^+$-implanted films decreased from 2.385 eV for the as-deposited film to 2.301 eV for maximum implantation whereas the optical absorption coefficient values increased with increasing implantation dose. Raman scattering due to the A$_l$(LO) phonon was observed at 299 cm$^{-1}$ in the as-deposited CdS film with a large full width at half maximum (FWHM). The Raman peak position did not change much whereas the FWHM increased with the ion dose. These are attributed to the effect of implantation induced lattice damage. A decrease in the area of the Raman peak of the CdS A$_l$(LO) mode is seen on implantation.