• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1514-1516
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• 1999

This paper covers our efforts to improve the low carrier mobility and light instability of hydrogenated amorphous silicon (a-Si:H) films with microcrystalline silicon $({\mu}c-Si)$ films. We successfully prepared ${\mu}c-Si$ films on $CaF_2$/glass substrate by decomposition of $SiH_4$ in RPCVD system. The $CaF_2$ films on glass served as a seed layer for ${\mu}c-Si$ film growth. The XRD analysis on $CaF_2$/glass illustrated a (111) preferred $CaF_2$ grains with the lattice mismatch less than 5 % of Si. We achieved ${\mu}c-Si$ films with a crystalline volume fraction of 61 %, (111) and (220) crystal orientations. grain size of $706\AA$, activation energy of 0.49 eV, and Photo/dark conductivity ratio of 124. By using a $CaF_2$/glass structure. we were able to achieve an improved ${\mu}c-Si$ films at a low substrate temperature of $300^{\circ}C$.

• Metals and materials international
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• 제24권6호
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• pp.1285-1292
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• 2018

Microstructural properties of as-grown and annealed CoCrFeMnNi high entropy alloy (HEA) oxynitride thin films were investigated. The CoCrFeMnNi HEA oxynitride thin film was grown by magnetron sputtering method using an air gas, and annealed under the argon plus air flow for 5 h at $800^{\circ}C$. The as-grown film was homogeneous and uniform composed of nanometer-sized crystalline regions mixed with amorphous-like phase. The crystalline phase in the as-grown film was face centered cubic structure with the lattice constant of 0.4242 nm. Significant microstructural changes were observed after the annealing process. First, it was fully recrystallized and grain growth happened. Second, Ni-rich region was observed in nanometer-scale range. Third, phase change happened and it was determined to be $Fe_3O_4$ spinel structure with the lattice constant of 0.8326 nm. Hardness and Young's modulus of the as-grown film were 4.1 and 150.5 GPa, while those were 9.4 and 156.4 GPa for the annealed film, respectively.

• 한국재료학회지
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• 제12권4호
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• pp.296-303
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• 2002

For potential application to quantum mechanical devices, nano-composite thin films, consisting of GaAs quantum dots dispersed in SiO$_2$ glass matrix, were fabricated and studied in terms of structural, chemical, and optical properties. In order to form crystalline GaAs quantum dots at room temperature, uniformly dispersed in $SiO_2$matrix, the composite films were made to consist of alternating layers of GaAs and $SiO_2$in the manner of a superlattice using RF magnetron sputter deposition. Among different film samples, nominal thickness of an individual GaAs layer was varied with a total GaAs volume fraction fixed. From images of High Resolution Transmission Electron Microscopy (HRTEM), the formation of GaAs quantum dots on SiO$_2$was shown to depend on GaAs nominal thickness. GaAs deposits were crystalline and GaAs compound-like chemically according to HRTEM and XPS analysis, respectively. From measurement of optical absorbance using a spectrophotometer, absorption edges were determined and compared among composite films of varying GaAs nominal thicknesses. A progressively larger shift of absorption edge was noticed toward a blue wavelength with decreasing GaAs nominal thickness, i.e. quantum dots size. Band gaps of the composite films were also determined from Tauc plots as well as from PL measurements, displaying a linear decrease with increasing GaAs nominal thickness.

• 동력기계공학회지
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• 제17권1호
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• pp.110-115
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• 2013

The electrochemical performance and microstructure of Al-Si, Al-Si/C was investigated as anode for lithium ion battery. The Al-Si nano composite with 5 : 1 at% ratio was prepared by arc-discharge nano powder process. However, some of problem is occurred, when Al nano composite was synthesized by this manufacturing. The oxidation film is generated around Al-Si particles for passivating processing in the manufacture. The oxidation film interrupts electrical chemistry reaction during lithium ion insertion/extraction for charge and discharge. Because of the existence the oxidation film, Al-Si first cycle capacity is very lower than other examples. Therefore, carbon synthsized by glucose ($C_6H_{12}O_6$) was conducted to remove the oxidation film covered on the composite. The results showed that the first discharge cycle capacity of Al-Si/C is improved to 113mAh/g comparing with Al-Si (18.6mAh/g). Furthermore, XRD data and TEM images indicate that $Al_4C_3$ crystalline exist in Al-Si/C composite. In addition the Si-Al anode material, in which silicon is more contained was tested by same method as above, it was investigated to check the anode capacity and morphology properties in accordance with changing content of silicon, Si-Al anode has much higher initial discharge capacity(about 500mAh/g) than anode materials based on Aluminum as well as the morphology properties is also very different with the anode based Aluminum.

• Corrosion Science and Technology
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• 제18권5호
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• pp.206-211
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• 2019

Silicon carbide (SiC) thin films become superhard when they have microstructures of nanocolumnar crystalline grains (NCCG) with an intergranular amorphous SiC matrix. We investigated the role of ion bombardment and deposition temperature in forming the NCCG in SiC thin films. A direct-current (DC) unbalanced magnetron sputtering method was used with pure Ar as sputtering gas to deposit the SiC thin films at fixed target power of 200 W and chamber pressure of 0.4 Pa. The Ar ion bombardment of the deposited films was conducted by applying a negative DC bias voltage 0-100 V to the substrate during deposition. The deposition temperature was varied between room temperature and $450^{\circ}C$. Above a critical bias voltage of -80 V, the NCCG formed, whereas, below it, the SiC films were amorphous. Additionally, a minimum thermal energy (corresponding to a deposition temperature of $450^{\circ}C$ in this study) was required for the NCCG formation. Transmission electron microscopy, Raman spectroscopy, and glancing angle X-ray diffraction analysis (GAXRD) were conducted to probe the samples' structural characteristics. Of those methods, Raman spectroscopy was a particularly efficient non-destructive tool to analyze the formation of the SiC NCCG in the film, whereas GAXRD was insufficiently sensitive.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.575-578
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• 2000

In this work, all solid-state thin film supercapacitor(TFSC) was fabricated using tungsten trioxide (WO$_3$) with a structure WO$_3$/LiPON/WO$_3$/Pt/TiO$_2$/Si (substrate). After TiO$_2$ was deposited on Si(100) wafer by d.c. reactive sputtering, the Pt current collector films were grown on TiO$_2$glue layer without breaking vacuum by d.c. sputtering. Fabrication conditions of WO$_3$ thin film were such that substrate temperature, working pressure, gas ratio of $O_2$/Ar and r.f. power were room temperature, 5 mTorr, 20% (O$_2$(8sccm)/Ar(32sccm)) and 200W, respectively. LiPON electrolyte film were grown on the WO$_3$ film using r.f. magnetron sputtering at room temperature. The XRD pattern of the as-deposited WO$_3$ thin film were shown no crystalline peak (amorphous). The SEM image of as-deposited WO$_3$ thin film showed that the surface is smooth and uniform. The capacitiy of as-fabricated TFSC was 0$\times$10$^{-2}$ F/$\textrm{cm}^2$-${\mu}{\textrm}{m}$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.153-153
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• 2011

유리나 폴리머를 기판으로 하는 TFT(Thin film transistor), solar cell에서는 낮은 공정 온도에서($200{\sim}500^{\circ}C$) amorphous semiconductor thin film을 poly-crystal semiconductor thin film으로 결정화 시키는 기술이 매우 중요하게 대두 되고 있다. Ge은 Si에 비해 높은 carrier mobility와 낮은 녹는점을 가지므로, 비 저항이 낮을 뿐만 아니라 더 낮은 온도에서 결정화 할 수 있다. 하지만 일반적으로 쓰이는 Ge의 결정화 방법은 비교적 높은 열처리 온도를 필요로 하거나, 결정화된 원소에 남아있는 metal이 불순물 역할을 한다는 문제점, 그리고 불균일한 결정크기를 만든다는 단점이 있었다. 그 중에서도 현재 가장 많이 쓰이고 있는 MIC, MILC는 metal과 a-Ge이 접촉되는 interface나, grain boundary diffusion에 의해 핵 생성이 일어나고, 결정이 성장하는 메커니즘을 가지고 있으므로 단순 증착과 열처리 만으로는 앞서 말한 단점을 극복하는데 한계를 가지고 있다. 이에 PIII&D 장비를 이용하면, 이온 주입된 원소들이 모재와 반응 할 수 있는 표면적이 커짐으로 핵 생성을 조절 할 수 있을 뿐만 아니라, 이온 주입 시 발생하는 self annealing effect로 결정 크기까지도 조절할 수 있다. 또한 이러한 모든 process가 한 진공 장비 내에서 이루어지므로 장비의 단순화와, 공정간 단계별로 발생하는 불순물과 표면산화를 막을 수 있으므로 절연체 위에 저항이 낮고, hall mobility가 높은 poly-crystalline Ge thin film을 만들 수 있다. 본 연구에서는, 주로 핵 생성과정에서 seed를 만드는 이온주입 조건과, 결정 성장이 일어나는 증착 조건에 따라서 Ge의 결정방향과 크기가 많은 차이를 보이는데, 이는 HR-XRD(High resolution X-ray Diffractometer)와 Raman spectroscopy를 이용하여 측정 하였으며, SEM과 AFM으로 결정의 크기와 표면 거칠기를 측정하였다. 또한 Hall effect measurement를 통해 poly-crystalline thin film 의 저항과 hall mobility를 측정하였다.

• Journal of Information Display
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• 제10권3호
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• pp.117-120
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• 2009

A new crystallization method for amorphous silicon, called selective area heating (SAH), was proposed. The purpose of SAH is to improve the reliability of amorphous silicon films with extremely low thermal budgets to the glass substrate. The crystallization time shortened from that of the conventional solid-phase crystallization method. An isolated thin heater for SAH was fabricated on a quartz substrate with a Pt layer. To investigate the crystalline properties, Raman scattering spectra were used. The crystalline transverse optic phonon peak was at about 519 $cm^{-1}$, which shows that the films were crystallized. The effect of the crystallization time on the varying thickness of the $SiO_2$ films was investigated. The crystallization area in the 400nm-thick $SiO_2$ film was larger than those of the $SiO_2$ films with other thicknesses after SAH at 16 W for 2 min. The results show that a $SiO_2$ capping layer acts as storage layer for thermal energy. SAH is thus suggested as a new crystallization method for large-area electronic device applications.

• 한국세라믹학회지
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• 제32권4호
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• pp.441-447
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• 1995

Ba0.65Sr0.35TiO3 (BST) thin films were deposited on Pt/SiO2/Si(100) substrate by rf magnetron sputtering. The substrate temperature changed from 35$0^{\circ}C$ to 55$0^{\circ}C$ and crystalline BST thin films were deposited above 45$0^{\circ}C$. Most of the films had (111) preferred orientation regardless of deposition temperature, but the films changed to (100) preferred orientation as gas pressure increased. The dielectric constant increased with increasing substrate temperature and film thickness, and ranged from 100 to 600 at room temperature. The leakage current increased as substrate temperature increased or as film thickness decreased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.122-125
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• 1995

Using metalorganic deposition technique, $La_2Ti_2O_{7}$ precursor solution was deposited on platinium coated SiO$_2$/SI(100) substrates by spin-coating process. Crystalline and crack-free films of ∼0.2$\mu\textrm{m}$ thickness were successfully fabricated on the above substrate from four different types of $La_2Ti_2O_{7}$ precursor solutions by proper heat treatment in the temperature range of $700^{\circ}C$∼$1200^{\circ}C$. Microstructure and X-ray diffraction analysis of $La_2Ti_2O_{7}$ thin film showed that the crystallization temperature and the preferred orientation of $La_2Ti_2O_{7}$ thin film were strongly dependent on the precursor used.