• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.310-313
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• 1993

The effect of Ni content in Cu underlayer on the magnetoresistance of Cu/Co artificial superlattice has been investigated. As the content of Ni increased, the preferred orientation of artificial superlattice changed from fec (100) to fcc (111) due to the change of the preferred orientation of the underlayer. When the content of Ni was 6 %, 26.7 % of magnetoresistance with 175 Oe of saturation field could be obtained in ${[Cu(19\AA)/Co(30\AA)]}_{20}|Cu-6%Ni(200\AA)/Si$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.460-460
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• 2013

본 연구는 Si (111) 기판위에 Ga 분자선량을 변화시켜 GaN 박막을 molecular beam epitaxy 법으로 성장하고, Schottky 장벽 다이오드를 제작한 후에 deep level transient spectroscopy (DLTS) 법을 통하여 깊은 준위 결함에 대하여 조사하였다. 성장 시 Ga 분자선량은, 그리고 Torr로 달리하여 V/III 비율을 변화시켰고, Schottky 장벽 다이오드 제작을 위하여 e-beam evaporator를 사용하여 metal을 증착하였다. Schottky 접촉에는 Ni (20 nm)/Au (100 nm)를 증착하였고, ohmic 접촉에는 Ti (20 nm)/Au (100 nm)를 증착하고 I-V, C-V 그리고 DLTS를 측정하였다. DLTS 신호를 통해 GaN 박막 성장 과정에서 형성되는 깊은 결함의 종류를 확인하였으며, 열처리 등의 처리 및 측정 조건변화에 따른 결함의 거동과 종류 및 원인에 대하여 분석 설명하였다.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1577-1579
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• 2003

AlN thin films are prepared on Si (111) substrate by RF magnetron sputtering. Two-step deposition method is proposed to obtain AlN thin films with high c-axis (002)-TC value and low surface roughnesses. For all the deposited AlN films, the c-axis (002)-orientation, surface mophology, and roughness are characterized in terms of deposition conditions FEAR devices with Al/AlN/Mo/Si(111) configuration are also fabricated. From the frequency response characteristics, the return loss and electromechanical coupling contant($k_t{^2}$) are estimated.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.155-155
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• 2000

Adsorption of alkali metals on a silicon surface has attracted much attention due to its importance in metal-semiconductor interface technology, In particular, the bonding nature of alkali metal to silicon substrate has been a focus of fundamental research efforts. We examined the adsorbed layer of Cs on a Si(111)-(7$\times$) surface by reactive ion scattering (RIS) of hyperthermal Cs+ beams. RIS from a Cs-adsorbed surface gives rise to Cs, representing pickup of surface Cs by Cs projectile. The Cs intensity is proportional to surface coverage of Cs at a high substrate temperature (473 K), while it varies anomalously with Cs coverage at low temperatures (130-170 K). This observation indicates that RIS selectively detects metallic Cs on surface, but discriminates ionic Cs. Transition from ionic to metallic Cs adlayer is driven by thermal diffusion of Cs and their clustering process.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.325-325
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• 2012

1차원구속 반도체인 nanowires (NWs)는 전기적, 광학적으로 일반 bulk구조와 다른 특성을 가지고 있어서 현재 많은 연구가 되고 있다. 일반적으로 NWs는 Au 등의 금속 촉매를 이용하여 성장을 하게 되는데 이때 촉매가 오염물로 작용을 해서 결함을 만들어서 bandgap내에 defect level을 형성하게 된다. 본 연구는 Si (111) 기판 위에 GaAs NWs 와 InAs NWs를 촉매를 이용하지 않고 성장 하였다. vapour-liquid-solid (VLS)방법으로 성장하는 GaAs NWs는 Ga의 droplet을 이용하게 되는데 Ga이 Si 기판위에 자연 산화막에 존재하는 핀홀(pinhole)로 이동하여 1차적으로 Ga droplet 형성하고 이후 공급되는 Ga과 As은 SiO2 보다 GaAs와 sticking coefficient 가 좋기 때문에 Ga drolept을 중심으로 빠른 선택적 성장을 하게 되면서 NWs로 성장을 하게 된다. 반면에 InAs NWs를 성장 할 시에 droplet 방법으로 성장을 하게 되면 NWs가 아닌 박막 형태로 성장을 하게 되는데 이것으로 InAs과 GaAs의 $SiO_2$와의 sticking coefficient 의 차이를 추측을 할 수 있다. InAs NWs는 GaAs NWs는 달리 native oxide를 이용하지 않고 InAs 과 Si 사이의 11.5%의 큰 lattice mismatch를 이용한다. 이종의 epitaxy 방법에는 크게 3종류 (Frank-van der Merwe mode, Stranski-Krastanov mode, Volmer-Weber mode)가 있는데 각기 다른 adatom 과 surface의 adhesive force로 나누어지게 된다. 이 중 Volmer-Weber mode epitaxy는 adatom 의 cohesive force가 surface와의 adhesive force보다 큰 경우 성장 되는 방식으로 InAs NWs 는 이 방식을 이용한다. 즉 droplet을 이용하지 않는 vapour-solid (VS) 방법으로 성장을 하였다. 이 때 In 의 migration을 억제하기 위해서 VLS mode 의 GaAs NWs 보다 As의 공급을 10배 이상 하였다. FE-SEM 분석 결과 GaAs NWs는 Ga droplet을 확인 할 수 있었고 InAs NWs는 droplet이 존재하지 않았다. GaAs와 InAs NW는 density와 length가 V/III가 높을수록 증가 하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.5
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• pp.486-492
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• 1999

The purpose of this research was to find out what is the dominant factor determining the $H_{ex}$ and the $H_C$ of Mn-Ir/Ni-Fe multilayers with different buffer layers. Regardless of (111) texture of Mn-Ir layer, all samples showed over the $H_{ex}$ of 155 Oe. We found out the $H_{ex}$ and the $H_C$ of Mn-Ir/Ni-Fe multilayers depend on interface morphology and grain size of Mn-Ir layer at the interface between Mn-Ir and Ni-Fe layers. The dependence of magnetroesistance ratio and coupling field on the thickness of ferromagnetic layer, thickness of Cu layer and different buffer layers have been studied. Maximum magnetoresistance ratio appeared for the sample Ta(5 nm)/Mn-Ir(10 nm)/Ni-Fe(7.5 nm)/Cu(2 nm)/Ni-Fe(6 nm)/Ta(5 nm)/Si. Magnetoresistance ratio may be related to grain of ferromagnetic layer. Coupling field may be related to the roughness and the grain size of ferromagnetic layer in the spin-valve multilayers.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.361-361
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• 2010

The separated quasi-one-dimensional ($7{\times}7$) and ($5{\times}5$) phases on vicinal Si(557) surfaces were successfully realized by changing the crystallographic orientation and thermal treatment conditions. A small change in the crystallographic orientation of the Si(557) surface stabilized the quasi-one-dimensional ($5{\times}5$) phase of a (111) facet on vicinal Si(557) surfaces and made it coexist with a quasi-one-dimensional ($7{\times}7$) phase after an optimal thermal treatment, whereas only the quasi-one-dimensional ($7{\times}7$) phase was stable on the Si(557) surface. Interestingly, this causes the (111) terraces with different widths (L) to prefer only one of the $5{\times}5$ (L=12) and $7{\times}7$ (L=9) phases resulting in long-range order of both phases along the step edge direction, which was observed by scanning tunneling microscopy (STM) and was supported by first principle calculations. In contrast, the quasi-one-dimensional ($5{\times}5$ and ($7{\times}7$) phases were arranged randomly across the step edge direction. The change of surface morphology of vicinal Si(557) surfaces will be discussed with STM images and theoretical calculations by changing crystallographic cutting angles and thermal treatment conditions.

• Journal of the Korean Vacuum Society
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• v.6 no.2
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• pp.165-171
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• 1997

If the thickness of Pd deposited is larger than 9$\AA$, its phase is $Pd_3Si$. This phase is followed by pure Pd phase with further deposition of Pd. Also, when the thickness of Pd deposited on top of Si(111) is larger than 1$\AA$, the phase of Pd-silicide formed is found to be Pd2Si. The full width at half maximum of Pd 3d core-levels increases with decreasing of Pd film thickness at low coverages ($\leq0.5\AA$). This is due to the formation of additional phase of Pd silicide, i.e. PdSi, in addition to $Pd_2Si$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.199-200
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• 2009

This paper describes the electrical properties of polycrystalline (poly) 3C-SiC thin films with different nitrogen doping concentrations. The in-situ-doped poly 3C-SiC thin films were deposited by using atmospheric-pressure chemical vapor deposition (APCVD) at $1200^{\circ}C$ with hexamethyldisilane (HMDS: $Si_2$ $(CH_3)_6)$ as a single precursor and 0 ~ 100 sccm of $N_2$ as the dopant source gas. The peaks of the SiC (111) and the Si-C bonding were observed for the poly 3C-SiC thin films grown on $SiO_2/Si$ substrates by using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses, respectively. The resistivity of the poly 3C-SiC thin films decreased from $8.35\;{\Omega}{\cdot}cm$ for $N_2$ of 0 sccm to $0.014\;{\Omega}{\cdot}cm$ with $N_2$ of 100 sccm. The carrier concentration of the poly 3C-SiC films increased with doping from $3.0819\;{\times}\;10^{17}$ to $2.2994\;{\times}\;10^{19}\;cm^{-3}$, and their electronic mobilities increased from 2.433 to $29.299\;cm^2/V{\cdot}S$.

• Journal of the Korean Ceramic Society
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• v.38 no.6
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• pp.531-536
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• 2001

SiCl$_4$/CH$_4$/H$_2$계를 사용한 플라즈마 화학증착법(PECVD)으로 실리콘(100) 기판 위에 3C-SiC막을 117$0^{\circ}C$~1335$^{\circ}C$의 온도범위에서 증착하였다. 증착온도, 유입가스비, R$_{x}$ [=CH$_4$/(CH$_4$+H$_2$)], 그리고 r.f. power를 변화시켜 증착막의 결정성에 대해 검토하였다. Thermal CVD에 비해 PECVD법은 박막의 증착속도를 향상시켰다. 증착된 3C-SiC은 (111) 면으로 최대의 우선배향성을 지님을 알 수 있었다. 실리콘 기판 위의 3C-SiC막의 결정성은 R$_{x}$값에 의존하였으며, R$_{x}$가 감소할수록 결정성이 더욱 향상되었다. Free Si가 3C-SiC막과 함께 증착되었으나, 증착온도와 r.f power가 증가함에 따라 free Si의 함량은 감소하였다. 증착온도 127$0^{\circ}C$, 유입가스비 R$_{x}$=0.04, r.f. power가 60W에서 비교적 결정성을 가진 3C-SiC막을 얻을 수 있었다.