그림자효과를 이용하여 증착한 타이타늄 박막의 미세구조 및 형상

한창석,진성윤,권혁구,Han, Chang-Suk,Jin, Sung-Yooun,Kwon, Hyuk-Ku 한국재료학회 2019 한국재료학회지 Vol.29 No.11

In order to observe the microstructure and morphology of porous titanium -oxide thin film, deposition is performed under a higher Ar gas pressure than is used in the general titanium thin film production method. Black titanium thin film is deposited on stainless steel wire and Cu thin plate at a pressure of about 12 Pa, but lustrous thin film is deposited at lower pressure. The black titanium thin film has a larger apparent thickness than that of the glossy thin film. As a result of scanning electron microscope observation, it is seen that the black thin film has an extremely porous structure and consists of a separated column with periodic step differences on the sides. In this configuration, due to the shadowing effect, the nuclei formed on the substrate periodically grow to form a step. The surface area of the black thin film on the Cu thin plate changes with the bias potential. It has been found that the bias of the small negative is effective in increasing the surface area of the black titanium thin film. These results suggest that porous titanium-oxide thin film can be fabricated by applying the appropriate oxidation process to black titanium thin film composed of separated columns.

기판의 결정구조에 따른 RF 스퍼터링 ZnO 박막의 성장과 미세구조 분석

유인성,소순진,박춘배,Yoo In-Sung,So Soon-Jin,Park Choon-Bae 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.5

To investigate the ZnO thin films which are interested in the next generation of short wavelength LEDs and Lasers, the ZnO thin films were deposited by RF sputtering system. At sputtering process of ZnO thin films, substrate temperature, work pressure respectively is $100^{\circ}C$ and 15 mTorr, and the purity of target is ZnO 5 N. The ZnO thin films were in-situ annealed at $600^{\circ}C$ in $O_2$ atmosphere. The thickness of ZnO thin films has implemented about $1.6{\mu}m$ at SEM analysis after in-situ annealing process. We have investigated the crystal structure of substrates, and so structural properties of ZnO thin films has estimate by using XRD, FWHM, FE-SEM and AFM. XRD and FE-SEM showed that ZnO thin films grown on substrates had a c-axis preferential orientation in the [0001] crystal direction. XPS spectra showed that ZnO thin film was showed a peak positions corresponding to the O1s and the Zn2p. As form above XPS, we showed that the atom ratio of Zn:O related 1:1.1504 on ZnO thin film, so we could obtained useful information for p-type ZnO thin film.

Micro/Nano-Mechanical Structure Fabricated by Transfer Printing

Takahiro Yamashita,Arata Kaneko,Kensaku Yoshino 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.

A fabrication of micro-electro-mechanical systems (MEMS) generally involves complicated conventional semiconductor processes. Simply micro/nano-structuring process is a technical issue on further wide range of MEMS application. This study proposes to applytransfer printing to fabricate a mechanical structure for MEMS elements. Some metals (Au, Cu and Ni) are previously deposited tobe thin-films on a micro-ridged poly-dimethyl-siloxane (PDMS) stamp, while a micro-grooved SU-8 is prepared as a substrate. Contact-and-release process allows the metal thin-film to be locally transferred from the micro-ridges of stamp to the micro-groovedsubstrate. The transferred Au and Ni thin-films successfully form to be an ultra-thin fixed beam, “cross-linked structure”, of whichthe thickness is less than 100 nm. The fabricated structure is applicable to a nano-scale mechanical oscillator. The production yieldof fixed beam increases with thin-film thickness and highly-dense of thin-film. The micro-roughness and hydrophobicity of stampenhance the production yield of ultrathin fixed beam. These experimental results clearly indicate that the proposed process isdominated by an adhesion force between the stamp and the thin-film as well as the mechanical strength of the thin-film. Nevertheless,it is confirmed the transfer printing process is effective for a fabrication of MEMS element.

Fabrication of c-axis-oriented K_(0.5)Bi_(4.5)Ti_4O_(15) Ferroelectric Thin Films by Using Chemical Solution Deposition

도달현,김상수,김진원,송태권,최병춘 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.31

The effects of crystal structure on the ferroelectric properties of K_(0.5)Bi_(4.5)Ti_4O_(15) (KBTi) thin films were investigated. Randomly-oriented and c-axis-oriented KBTi thin films were prepared by using a chemical solution deposition method. Both thin films were annealed at 750 ℃ under an oxygen atmosphere. The randomly-oriented thin film showed better ferroelectric properties than the c-axis-oriented film. The remnant polarization (2P_r) of the randomly-oriented thin film was 13.5 μC/cm_2 at an applied electric field of 233 kV/cm, which is larger than that of the c-axis-oriented thin film, 4.8 μC/cm^2. This indicates that the polarization vector is not along the c-axis. The randomly-oriented thin film also showed a lower leakage current density than the c-axis-oriented thin film, as well as good fatigue endurance.

Basic Study on RF Characteristics of Thin-Film Transmission Line Employing ML/CPW Composite Structure on Silicon Substrate and Its Application to a Highly Miniaturized Impedance Transformer

Jeong, Jang-Hyeon,Son, Ki-Jun,Yun, Young The Korean Institute of Electrical and Electronic 2015 Transactions on Electrical and Electronic Material Vol.16 No.1

A thin-film transmission line (TFTL) employing a microstrip line/coplanar waveguide (ML/CPW) was fabricated on a silicon substrate for application to a miniaturized on-chip RF component, and the RF characteristics of the device with the proposed structure were investigated. The TFTL employing a ML/CPW composite structure exhibited a shorter wavelength than that of a conventional coplanar waveguide and that of a thin-film microstrip line. When the TFTL with the proposed structure was fabricated to have a length of ${\lambda}/8$, it showed a loss of less than 1.12 dB at up to 30 GHz. The improvement in the periodic capacitance of the TFTL caused for the propagation constant, ${\beta}$, and the effective permittivity, ${\varepsilon}_{eff}$, to have values higher than those of a device with only a conventional coplanar waveguide and a thin film microstrip line. The TFTL with the proposed structure showed a ${\beta}$ of 0.53~2.96 rad/mm and an ${\varepsilon}_{eff}$ of 22.3~25.3 when operating from 5 to 30 GHz. A highly miniaturized impedance transformer was fabricated on a silicon substrate using the proposed TFTL for application to a low-impedance transformation for broadband. The size of the impedance transformer was 0.01 mm2, which is only 1.04% of the size of a transformer fabricated using a conventional coplanar waveguide on a silicon substrate. The impedance transformer showed excellent RF performance for broadband.

Structural and Electrical Investigations of Aurivillius-phase La- and V-doped Bi5FeTi3O15 Thin Films

김해진,김진원,최지야,김은주,라그하반,김상수 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.12

Bi5FeTi3O15 (BFTO), Bi4.25La0.75FeTi3O15 (BLFTO), Bi5FeTi2.97V0.03O15+ (BFTVO) andBi4.25La0.75FeTi2.97V0.03O15+ (BLFTVO) thin films were deposited on Pt(111)/Ti/SiO2/Si(100)substrates by using a chemical solution deposition method. The thin films were well crystallizedand randomly oriented, with no detectable impurities and no secondary phases. The effects of Laand V doping alone and of co-doping with La and V on the structural, electrical and ferroelectricproperties of Bi5FeTi3O15 thin films were investigated. Among the thin films, superior electricalproperties were observed in the BLFTVO thin film. The BLFTVO thin film exhibited a low leakagecurrent density of 1.7 × 10−6 A/cm2 at an electric field of 100 kV/cm, typical hysteresis loops, ahigh dielectric constant and a low loss tangent.

Influence of Cr-doping on the Structural and the Optical Properties of ZnO Thin Films Prepared by Sol-gel Spin Coating

김익현,Daeho Kang,임재영,남기웅,윤현식,김소람,김종수,김진수 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.1

Thin films of undoped ZnO and Cr-doped ZnO were deposited by sol-gel spin coating. Thestructural and the optical properties of Cr-doped ZnO thin films with different concentrations of Cr(0-2.5 at.% relative to Zn) were studied by using X-ray diffraction (XRD) and photoluminescence(PL). The XRD showed that the thin films grew with a preferred c-axis orientation. No traces ofthe Cr metal, oxides, or a binary Zn-Cr phase were detected. This means that the addition of Crinto the ZnO matrix preserved the formation of the wurtzite structure of ZnO. However, increasingthe amount of Cr dopant in the ZnO thin films caused distortion due to the intercalation of thedopant atoms into the wurtzite structure. The PL spectra showed a blue shift in the near-band-edgeemission and a decrease in the deep-level emission upon increasing the amount of Cr doping. Thenarrowest full width at half maximum (FWHM) was observed in ZnO thin films with 2.5 at.% Crdoping. The FWHM gradually decreased upon further increasing the Cr concentration.

Basic Study on RF Characteristics of Thin-Film Transmission Line Employing ML/CPW Composite Structure on Silicon Substrate and Its Application to a Highly Miniaturized Impedance Transformer

정장현,송기준,윤영 한국전기전자재료학회 2015 Transactions on Electrical and Electronic Material Vol.16 No.1

A thin-film transmission line (TFTL) employing a microstrip line/coplanar waveguide (ML/CPW) was fabricated ona silicon substrate for application to a miniaturized on-chip RF component, and the RF characteristics of the devicewith the proposed structure were investigated. The TFTL employing a ML/CPW composite structure exhibited ashorter wavelength than that of a conventional coplanar waveguide and that of a thin-film microstrip line. Whenthe TFTL with the proposed structure was fabricated to have a length of λ/8, it showed a loss of less than 1.12 dBat up to 30 GHz. The improvement in the periodic capacitance of the TFTL caused for the propagation constant,β, and the effective permittivity, εeff, to have values higher than those of a device with only a conventional coplanarwaveguide and a thin film microstrip line. The TFTL with the proposed structure showed a β of 0.53~2.96 rad/mm andan εeff of 22.3~25.3 when operating from 5 to 30 GHz. A highly miniaturized impedance transformer was fabricatedon a silicon substrate using the proposed TFTL for application to a low-impedance transformation for broadband. The size of the impedance transformer was 0.01 mm2, which is only 1.04% of the size of a transformer fabricatedusing a conventional coplanar waveguide on a silicon substrate. The impedance transformer showed excellent RFperformance for broadband.

Properties of hafnium-aluminum-zinc-oxide thin films for the application of oxide-transistors

Lee, Sang-Hyuk,Jun, Hyun-Sik,Park, Ju-Hee,Kim, Won,Oh, Saeroonter,Park, Jin-Seok Elsevier 2016 THIN SOLID FILMS - Vol.620 No.-

<P><B>Abstract</B></P> <P>Hafnium-aluminum zinc oxide (HAZO) films as an active layer of oxide-transistors with different hafnium (Hf) contents were deposited via co-sputtering of separate targets. The effects of the sputtering power during co-sputtering on the structural, optical, electrical, and chemical properties of the HAZO films were examined. As the sputtering power increased, the structure of the HAZO films changed from polycrystalline to amorphous, and the HfO bonds in the HAZO films increased, but the ZnO bonds decreased. Also, a bottom-gate-type thin-film transistor (TFT) using the HAZO film as its channel layer was fabricated and characterized. The TFTs using HAZO layer at room temperature as channel layer exhibited the device characteristics, such as a field effect mobility of 0.45cm<SUP>2</SUP>/V·s, a threshold voltage of 17.18V, a subthreshold swing of 0.85V/decade, an on/off current ratio of 3.68×10<SUP>7</SUP>, and a visible transmittance of 82.7%. It was discovered that the changes of the electrical characteristics of the HAZO TFTs were closely related to the changes of the ZnO/HfO bonding ratio.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hafnium-aluminum-zinc-oxide (HAZO) films were deposited via co-sputtering. </LI> <LI> Hf content was controlled by varying the sputtering powers of Hf or HfO<SUB>2</SUB> targets. </LI> <LI> Chemical, structural, and optical properties of HAZO films were analyzed. </LI> <LI> The properties of HAZO films strongly depended on the Hf or HfO<SUB>2</SUB> sputtering power. </LI> <LI> Effects of Hf contents on the characteristics of HAZO-TFTs have been analyzed. </LI> </UL> </P>

졸겔공정을 이용한 $Bi_{4-x}Sm_xTi_3O_{12}(0<\leqx\geq2)$ 박막제조 및 특성평가

이창민,고태경 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.8

Thin films of Bi4-xSmxTi3O12(0$\leq$x$\leq$2) were prepared on Pt/Ti/SiO2/Si(100) at $700^{\circ}C$ using spin-coating with sols derived from Bi-Sm-Ti complex alkoxides. From X-ray diffraction analysis, it was observed that Sm-substituted phases resembled ferroelectric Bi4Ti3O12 in structure. Variations of their lattice parameters depending on the amount of Sm-substitution showed that an anomalous structural distortion might exist at x=1. The grain sizes of the thin films decreased from 0.115 ${\mu}{\textrm}{m}$ to 0.078${\mu}{\textrm}{m}$ with increasing the amount of Sm-substitution. The dielectric constants and the remanent polarizations of the thin films decreased with increasing the amount of the Sm-substitution, which were related to decrease of the stereo-active Bi3+ ion contributing to polarization. However, these values were exceptionally high at x=1, compared to those of the other substituted phases. Such an anomaly suggests that the phase of x=1 has 1:1 chemical ordering between Sm and Bi in structure. The thin films of all compositions except x=2 showed ferroelectricity. The thin film of x=2 was paraelectric, whose grains were too fine to exhibit ferroelectricity.