• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.398.1-398.1
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• 2014

The $Cu_2ZnSnSe_4$ (CZTSe) thin films solar cell is one of the next generation candidates for photovoltaic materials as the absorber of thin film solar cells because it has optimal bandgap (Eg=1.0eV) and high absorption coefficient of $10^4cm^{-1}$ in the visible length region. More importantly, CZTSe consists of abundant and non-toxic elements, so researches on CZTSe thin film solar cells have been increasing significantly in recent years. CZTSe thin film has very similar structure and properties with the CIGS thin film by substituting In with Zn and Ga with Sn. In this study, As-deposited CZTSe thin films have been deposited onto soda lime glass (SLG) substrates at different deposition condition using Pulsed Laser Deposition (PLD) technique without post-annealing process. The effects of deposition conditions (deposition time, deposition temperature) onto the structural, compositional and optical properties of CZTSe thin films have been investigated, without experiencing selenization process. The XRD pattern shows that quaternary CZTSe films with a stannite single phase. The existence of (112), (204), (312), (008), (316) peaks indicates all films grew and crystallized as a stannite-type structure, which is in a good agreement with the diffraction pattern of CZTSe single crystal. All the films were observed to be polycrystalline in nature with a high (112) predominant orientation at $2{\theta}{\sim}26.8^{\circ}$. The carrier concentration, mobility, resistivity and optical band gap of CZTSe thin films depending on the deposition conditions. Average energy band gap of the CZTSe thin films is about 1.3 eV.

• Korean Journal of Materials Research
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• v.26 no.1
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• pp.47-53
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• 2016

Silicon nitride ($SiN_x:H$) films made by plasma enhanced chemical vapor deposition (PECVD) are generally used as antireflection layers and passivation layers on solar cells. In this study, we investigated the properties of silicon nitride ($SiN_x:H$) films made by PECVD. The passivation properties of $SiN_x:H$ are focused on by making the antireflection properties identical. To make equivalent optical properties of silicon nitride films, the refractive index and thickness of the films are fixed at 2.0 and 90 nm, respectively. This limit makes it easier to evaluate silicon nitride film as a passivation layer in realistic application situations. Next, the effects of the mixture ratio of the process gases with silane ($SiH_4$) and ammonia ($NH_3$) on the passivation qualities of silicon nitride film are evaluated. The absorption coefficient of each film was evaluated by spectrometric ellipsometry, the minority carrier lifetimes were evaluated by quasi-steady-state photo-conductance (QSSPC) measurement. The optical properties were obtained using a UV-visible spectrophotometer. The interface properties were determined by capacitance-voltage (C-V) measurement and the film components were identified by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectroscopy detection (RBS) - elastic recoil detection (ERD). In hydrogen passivation, gas ratios of 1:1 and 1:3 show the best surface passivation property among the samples.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.144-144
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• 2012

최근 폴리머를 기판으로 하는 고속 Flexible TFT (Thin film transistor)나 고효율의 박막 태양전지(Thin film solar cell)를 실현시키기 위해 낮은 비저항(resistivity)을 가지며, 높은 홀 속도(carrier hall mobility)와 긴 이동거리를 가지는 다결정 반도체 박막(poly-crystalline semiconductor thin film)을 만들고자 하고 있다. 지금까지 다결정 박막 반도체를 만들기 위해서는 비교적 높은 온도에서 장시간의 열처리가 필요했으며, 이는 폴리머 기판의 문제점을 야기시킬 뿐 아니라 공정시간이 길다는 단점이 있었다. 이에 반도체 박막의 재결정화 온도를 낮추어 주는 metal (Al, Ni, Co, Cu, Ag, Pd, etc.)을 이용하여 결정화시키는 방법(MIC)이 많이 연구되어지고 있지만, 이 또한 재결정화가 이루어진 반도체 박막 안에 잔류 금속(residual metal)이 존재하게 되어 비저항을 높이고, 홀 속도와 이동거리를 감소시키는 단점이 있다. 이에 본 실험은, 종래의 MIC 결정화 방법에서 이용되어진 금속 증착막을 이용하는 대신, HIPIMS (High power impulse magnetron sputtering)와 PIII&D (Plasma immersion ion implantation and deposition) 공정을 복합시킨 방법으로 적은 양의 알루미늄을 이온주입함으로써 재결정화 온도를 낮추었을 뿐 아니라, 잔류하는 금속의 양도 매우 적은 다결정 반도체 박막을 만들 수 있었다. 분석 장비로는 박막의 결정화도를 측정하기 위해 GIXRD (Glazing incident x-ray diffraction analysis)와 Raman 분광분석법을 사용하였고, 잔류하는 금속의 양과 화학적 결합 상태를 알아보기 위해 XPS (X-ray photoelectron spectroscopy)를 통한 분석을 하였다. 또한, 표면 상태와 막의 성장 상태를 확인하기 위하여 HRTEM(High resolution transmission electron microscopy)를 통하여 관찰하였다.

• Current Photovoltaic Research
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• v.3 no.3
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• pp.101-105
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• 2015

ZnO is gathering great interest for large square optoelectrical devices of flat panel display (FHD) and solar cell as a transparent conductive oxide (TCO). Herewith, Mg and IIIA (Al, In) co-doped ZnO films were prepared on SLG substrate using RF magnetron sputtering system. The effect of variation of atomic weight % of Mg and ZnO have been investigated. The atomic weight % Al and In are of 3% and kept constant throughout. The numbers of samples were prepared according to their different contents, which are $M_{3%}AZO_{94%}$, $M_{4%}AZO_{93%}-(MAZO)$ and $M_{3%}IZO_{94%}$, $M_{4%}IZO_{93%}-(MIZO)$ respectively. A RF power of 225 W and working pressure of 6 m Torr was used for the deposition at $300^{\circ}C$. All of the two thin film show good uniformity in field emission scanning electron microscopy image. $M_{3%}AZO_{94%}$ thin film shows overall better performance among the all. The film shows the best lowest resistivity, carrier concentration, mobility and Sheet resistance and is found to be are of $8.16{\times}10^{-4}{\Omega}cm$, $4.372{\times}10^{20}/cm^3$, $17.5cm^2/vs$ and $8.9{\Omega}/sq$ respectively. Also $M_{3%}AZO_{94%}$ thin film shows the relatively high optical band gap energy of 3.7 eV with high transmittance more than 80% in visible region required for the better solar cell performance.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.491-495
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• 2005

(Zn,Mg)O (ZMO) thin films doped with Ga $(0\~0.03mol\%)$ in the target source were prepared by pulsed laser deposition on c-plane sapphire substrates at $500^{\circ}C$, and the effect of Ga contents on the properties of the electrical, optical and crystal properties of the deposited films was investigated. From X-ray diffraction patterns, ZMO film doped with $0.02 mol\%$ Ga showed crystal structure with c-axis preferred orientation, showing only the (0002) and (0004) diffraction peaks. In contrast, ZMO film doped with $Ga=0.03 mol\%$ showed a randomly oriented crystal structure. All the samples were highly transparent, showing the transmittance values of above $85\%$ in the visible region. For all the Ga doped ZMO films, the value of energy band gap was found to be about 3.5 eV, regardless of their Ga contents. From the Hall measurements, the resistivity and the carrier density for the ZMO film doped with $0.01 mol\%$ Ga were about $5\times10^{-4}\Omega-cm$ and $2\times10^{21}cm^{-3}$, respectively.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.4
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• pp.161-168
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• 2001

Organic thin film transitors(TFTs) are of interest for use in broad area electronic applications. For example, in active matrix liquid crystal displays(AMLCDs), organic TFTs would allow the use of inexpensive, light-weight, flexible, and mechanically rugged plastic substrates as an alternative to the glass substrates needed for commonly used hydrogenated amorphous silicon(a-Si:H). Recently pentacene TFTs with carrier field effect, mobility as large as 2 $cm^2V^{-1}s^{-1}$ have been reported for TFTs fabricated on silicon substrates, and it is higher than that of a-Si:H. But these TFTs are fabricated on silicon wafer and $SiO_2$ was used as a gate insulator. $SiO_2$ deposition process requires a high insulator which is polyimide and photo acryl. We investigated trasfer and output characteristics of the thin film transistors having active layer of pentacene. We calculated field effect mobility and on/off ratio from transfer characteristics of pentacene thin film transistor, and measured IR absorption spectrum of polymide used as the gate dielectric layer. It was found that using the photo acryl as a gate insulator, threshold voltage decreased from -12.5 V to -7 V, field effect mobility increased from 0.012 $cm^2V^{-1}s^{-1}$ to 0.039 $cm^2V^{-1}s^{-1}$ , and on/off current ratio increased from $10^5\;to\;10^6$. It seems that TFTs using photo acryl gate insulator is apt to form channel than TFTs using polyimide gate insulator.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.127.1-127.1
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• 2011

In this paper, ZnO:Al thin films with c-axis preferred orientation were prepared on Soda lime glass substrates by RF magnetron sputtering technique. AZO thin film were prepared in order to clarify optimum conditions for growth of the thin film depending upon process, and then by changing a number of deposition conditions and substrate temperature conditions variously, structural and electrical characteristics were measured. For the manufacture of the AZO were vapor-deposited in the named order. It is well-known that post-annealing is an important method to improve crystal quality. For the annealing process, the dislocation nd other defects arise in the material and adsorption/decomposition occurs. The XRD patterns of the AZO films deposited with grey theory prediction design, annealed in a vacuum ambient($2.0{\times}10-3$Torr)at temperatures of 200, 300, 400 and $500^{\circ}C$ for a period of 30min. The diffraction patterns of all the films show the AZO films had a hexagonal wurtzite structure with a preferential orientation along the c-axis perpendicular to the substrate surface. As can be seen, the (002)peak intensities of the AZO films became more intense and sharper when the annealing temperature increased. On the other hand, When the annealing temperature was $500^{\circ}C$ the peak intensity decreased. The surface morphologies and surface toughness of films were examined by atomic force microscopy(AFM, XE-100, PSIA). Electrical resistivity, Gall mobility and carrier concentration were measured by Hall effect measuring system (HL5500PC, Accent optical Technology, USA). The optical absorption spectra of films in the ultraviolet-visibleinfrared( UV-Vis-IR) region were recorder by the UV spectrophotometer(U-3501, Hitachi, Japan). The resistivity, carrier concentration, and Hall mobility of ZnS deposited on glass substrate as a function of post-annealing.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.1
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• pp.6-13
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• 2010

In this study, Ga-doped ZnO (GZO) thin films have been fabricated on Eagle 2000 glass substrates at various substrate temperatures $100{\sim}400^{\circ}C$ and thin film thickness by RF magnetron sputtering in order to investigate the structural, electrical, and optical properties of the GZO thin films. It is observed that all the thin films exhibit c-axis orientation and a (002) diffraction peak only. The GZO thin films, which were deposited at $T=300^{\circ}C$ and 400 nm, shows the highest (002) orientation, and the full width at half maximum (FWHM) of the (002) diffraction peak is $0.4^{\circ}$. AFM analysis shows that the formation of relatively smooth thin films are obtained. The lowest resistivity ($8.01{\times}10^{-4}\;{\Omega}cm$) and the highest carrier concentration ($3.59{\times}10^{20}\;cm^{-3}$) are obtained in the GZO thin films deposited at $T=300^{\circ}C$ and 400 nm. The optical transmittance in the visible region is approximately 80 %, regardless of process conditions. The optical band-gap shows the slight blue-shift with increase in doping which can be explained by the Burstein-Moss effect.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.20-26
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• 2001

The deposition characteristics of MOCVO Cu using the (hfac)Cu(I) (1,5-DMCOD)(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato Cu(I) 1,5-dimethyl-cyclooctadine) as a precursor have been investigated in terms of the effects of hydrogen and H(hfac) ligand addition with He carrier gas. MOCVD Cu using a Helium carrier gas showed a low deposition rate (20~$125{\AA}/min$) at the substrate temperature range of 180~$230^{\circ}C$. Moreover, the Cu film deposited at 19$0^{\circ}C$ was very thin (~$700{\AA}$) and showed the lowest resistivity value of $2.8{\mu}{\Omega}-cm$. The deposition rate of MOCVD Cu using $H_2$or H(hfac) addition was significantly enhanced especially at the low temperature region (180~$190^{\circ}C$). Furthermore, thinner Cu films (~$500{\AA}$) provided low resistivity (3.6~$2.86{\mu}{\Omega}-cm$). From surface reflectance measurement, very thin films deposited by using different gas system revealed good surface morphology comparable with sputtered Cu film ($300^{\circ}C$, vacuum-anneal). Hence, Cu film using (hfac)Cu(1,5-DMCOD) as a precursor is expected as a good seed layer in the electrochemical deposition process for Cu metallization.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.296-301
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• 2009

An inductively coupled plasma assisted atomic layer deposition(ICP-ALD) system has been constructed for the deposition of ZnO thin films, and various experiments of ZnO thin films on p-type Si(100) substrates have been carried out to find the self-limiting reaction conditions for the ICP-ALD system under non-plasma circumstances. Diethyl zinc[$Zn(C_2H_5)_2$, DEZn] was used as the zinc precursor, $H_2O$ as the oxidant, and Ar as the carrier and purge gas. At the substrate temperature of $150^{\circ}C$, atomic layer deposition conditions based on self-limiting surface reaction were successfully obtained by series of experiments through the variation of exposure times for DEZn, $H_2O$, and Ar. ZnO deposition was repeated at different substrate temperatures of $90{\sim}210^{\circ}C$. As a result, the thermal process window(ALD window) for ZnO thin films was observed to be $110{\sim}190^{\circ}C$ and the average growth rate was measured to be constant of 0.29 nm/cycle. Properties of the film's microstructure and composition(Zn, O, etc.) were also studied. As the substrate temperature increases, the crystallinity was improved and ZnO(002) peak became dominant. The films deposited at all temperatures were high purity, and the films deposited at high temperatures had the composition ratio between Zn and O closer to one of a stable hexagonal wurtzite structure.