• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.466-468
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• 2012

Amorphous InGaZnO (${\alpha}$-IGZO) thin-film transistors (TFTs) are are very promising due to their potential use in thin film electronics and display drivers [1]. However, the stability of AOS-TFTs under the various stresses has been issued for the practical AOSs applications [2]. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability [3]. Nomura et al. reported that these deep defects are located in the surface layer of the ${\alpha}$-IGZO channel [4]. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process [5]. It is well known that these trap states can influence on the performances and stabilities of ${\alpha}$-IGZO TFTs. Nevertheless, it has not been reported how these defect states are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films [6-10] and can change the defect states of ${\alpha}$-IGZO thin film. In this paper, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in ${\alpha}$-IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process [9-10] to eliminate the NOI bombardment effects and present how much to be improved the instability of ${\alpha}$-IGZO TFTs by this new deposition method.

• 대한화학회지
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• 제57권6호
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• pp.677-683
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• 2013

A theoretical study of the electronic structures of $TiC_{1-x}$ and $Ti_{1-x}W_xC$ (x = 0, 0.25) is presented. The density of states and crystal orbital overlap population calculations were used to interpret variations of elastic properties induced by carbon vacancies and alloying substitutions. Our results show why the introduction of vacancies into TiC reduces bulk moduli, while W substitution at a Ti site increases the elastic modulus. The effect of the point defects on the bonding in TiC is investigated by means of extended Huckel tight-binding band calculations.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.129-134
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• 2004

The development of fabrication processes of polycrystalline-silicon-thin-film transistors (poly-Si TFTs) at low temperatures is reviewed. Rapid crystallization through laser-induced melt-regrowth has an advantage of formation of crystalline silicon films at a low thermal budget. Solid phase crystallization techniques have also been improved for low temperature processing. Passivation of $SiO_2$/Si interface and grain boundaries is important to achieve high carrier transport properties. Oxygen plasma and $H_2O$ vapor heat treatments are proposed for effective reduction of the density of defect states. TFTs with high performance is reported.

• EDISON SW 활용 경진대회 논문집
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• 제2회(2013년)
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• pp.243-245
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• 2013

Topological insulator (TI) has non-trivial metallic surface states and has provoked many studies of property of this metarial. One of TI, $Bi_2Se_3$ is the promising metarial due to application of quantum devices. We investigate the effect of Ag adatom in the $Bi_2Se_3$ (111) surface. The silver atom prefers to locate within the vdW gap between the QLs rather than on the top surface. The effect of Ag adsorption is the rise of the Fermi level implying that the adsorbed Ag atoms behave like electron donors.

• Bulletin of the Korean Chemical Society
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• 제19권6호
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• pp.628-634
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• 1998

The properties of the n-type impurities nitrogen and phosphorus in diamond have been investigated by means of electronic band structure calculations within the framework of the semiempirical extended Huckel tight-binding method. For diamond with the nitrogen and phosphorus substitutional impurities, calculated density of states shows the impurity level deep in the band gap. This property can be derived from the substantial <111> relaxation of the impurity and nearest-neighbor carbon atoms, which is associated with the population of an antibonding orbital between them. The passivated donor property of the P-vacancy complex which lies deep in the gap is also discussed.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.609-614
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• 2013

Extended H$\ddot{u}$ckel tight-binding band structure calculations are used to address the chemical bonding and elastic properties of $Zr_2AC$ (A=Al, Si, P, and S). Elastic properties are interpreted by analyzing the density of states and the crystal orbital overlap population for the respective phases. Our results show that the bulk modulus of these ternary compounds is determined by the strength of Zr-A bonds.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.155-156
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• 2000

We propose a new in-situ fluorine passivation of poly-Si TFTs by excimer laser annealing to reduce the trap density and improve the reliability significantly. This improvement is due to the formation of stronger Si-F bonds than Si-H bonds which passivate the trap states.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.593-596
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• 1998

Effects of current re-stress after anneal on leakage current and trapped charges in oxides are investigated. Current stress on 6 nm thick oxide has generated mostly positive traps within the oxide resulting in leakage currents. The interface states generated are several orders of magnitude smaller, determined by C-V and charge pumping method. Annealing has eliminated only the charged traps not the neutral traps, thus the leakage current and trap density are increased when the oxides are re-stressed.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4155-4160
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• 2012

We characterized the physisorption of p-iodo-phenyl octadecyl ether molecules (I-POE) onto superlattice regions of graphite surfaces using scanning tunneling microscopy (STM). The formation of self-organized I-POE monolayers does not affect the overall structures of moir$\acute{e}$ patterns and their modulation periods. However, the packing density of the I-POE monolayer and the orientations of lamella structures were sensitive to the underlying superlattice structure. Depending on the bias voltage, the STM images selectively showed moir$\acute{e}$ pattern, I-POE layer, or both. Reflecting the local density of states at a certain energy level, the STM images thereby revealed the relative energy level scale of the superlattice with respect to the molecular orbitals of I-POE.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.373-377
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• 2015

이 연구에서는 원자 궤도 함수 기반 DFT 전자구조 계산을 이용해서 최근 각광받고 있는 이차원 물질인 MoS2 monolayer의 S 자리와 Mo 자리에 각각 전자가가 다른 원자를 치환하였을 때의 도핑 특성을 Density of States (DOSs)와 밴드구조 등의 전자구조를 통해 분석해 보았다. S자리에 Cl, Si, I, B, C, Mo 자리에는 Hf, Ta, 그리고 Re을 치환해 보았으며 계산 결과 S자리에 Cl을 치환했을 때 가장 얕은 acceptor level (VBM으로부터 0.08 eV)이 형성되었으며, Mo자리에 Re를 치환했을 때에는 resonant state를 형성하였다. 또한 Mo자리에 Ta를 치환했을 ? 가장 얕은 donor level (CBM으로부터 0.02 eV)가 형성되었다.