서지주요정보
운반기체를 쓰지않은 MOCVD에 의한 $PbTiO_3$ 얇은 막의 합성 = A synthesis of $PbTiO_3$ thin films by MOCVD without carrier gas
서명 / 저자 운반기체를 쓰지않은 MOCVD에 의한 $PbTiO_3$ 얇은 막의 합성 = A synthesis of $PbTiO_3$ thin films by MOCVD without carrier gas / 변철수.
저자명 변철수 ; Byun, Chul-Soo
발행사항 [대전 : 한국과학기술원, 1997].
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소장정보

등록번호

8008152

소장위치/청구기호

학술문화관(문화관) 보존서고

DNE 97009

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초록정보

A new metal-organic chemical vapor deposition(MOCVD) process "without carrier gas" was developed in the deposition of $PbTiO_3$ thin films. Tetraethyl-lead, Titanium tetra-isopropoxide, and pure oxygen were used as precursors. Substrates used were Si, $TiO_2$/Si, and Pt/$SiO_2$/Si. Phase formation in the deposited thin films was investigated by X-ray diffraction pattern. Chemical composition of the thin film was investigated by energy dispersive analysis of X-ray, Auger electron spectroscopy, and secondary ion mass spectroscopy. Microstructure of the thin film was characterized by scanning electron microscopy and transmission electron microscopy. Electrical properties was investigated by capacitance-voltage plot and displacement-electric field characteristics. Since $PbTiO_3$ is a stoichiometry compound of PbO and $TiO_2$, the individual growth behavior of PbO and $TiO_2$ thin film was investigated formerly as a preliminary experiment. PbO grown on Si was crystalline even at $500\circ\,C$. However, on substrates of which upper surface temperature was far below than that of heating block, a huge growth rate ($100\mu m$/h) was found, for which the volatility and thermal diffusion of PbO would have been responsible. $TiO_2$ thin films grown on Si showed anatase-rutile phase transition at much low temperature of $400\circ\,$, which was explained by the source effect. The growth rate of $TiO_2$ was numerically analyzed by using the Patankar program and a suggested diffusion model in this work. In the expression of diffusion flux of a species,the concentration gradients of other species as well as the own species were included all together. In the growth of $PbTiO_3$ thin films, the effects of substrate temperature, Pb/Ti mass flow ratio, and growth rate on the formation of phases in Pb-Ti-O thin films were investigated. The consumption rate of Pb precursor relative to that of Ti precursor in this work was higher than that with carrier gas for the formation of $PbTiO_3$ phases. Perovskite structures have been obtained with all kinds of investigated substrates at low temperature($450\circ\,C$). Growth rates were as high as $5.0\mu m$/h and $9.2\mu m$/h on Si and $Pt/SiO_2/Si$, respectively. Suppression of additional impinging flux by excluding carrier gas is considered to have resulted in the synthesis of the perovskite structure at low temperature as well as the high growth rate. It was found that $TiO_2$ intermediate layer was an effective diffusion barrier which suppressed the interdiffusion of Pb and Si. Electrical properties of deposited thin films were evaluated. Among two types of $PbTiO_3$ thin films prepared on $Pt/SiO_2/Si$ substrates with metal-ferroelectric-metal structure, one type which was in-situ deposited at $450\circ\,C$ and the other type which was post-annealed at $650\circ\,C$ after deposited at $450\circ\,C$, only the film post-annealed at $650\circ\,C$ displayed ferroelectricity although both types of films possessed the perovskite structure. The existence of domain wall structure which is generated when cooling down from above Curie temperature(~$490\circ\,C$) to below Curie temperature was correlated with the ferroelectricity which was revealed only at the specimen post-annealed at $650\circ\,C$. The effect of $TiO_2$ buffer layer on the C-V characteristics in the $PbTiO_3/TiO_2/Si$ capacitors with metal-ferroelectric-insulator- semiconductor structure was investigated. If $TiO_2$ layer had a sufficient thickness and was grown at the temperature low enough to prevent the interface reactions with the Si, the C-V hysteresis showed the normal behavior. It was concluded that an MOCVD technique without carrier gas is a suitable method in the deposition of thin films and the suggested model in the expression of diffusion flux well predicted the mass transport phenomena even in the case that the concentration of precursors was very high.

서지기타정보

서지기타정보
청구기호 {DNE 97009
형태사항 xiv, 110 p. : 삽도, 사진 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Chul-Soo Byun
지도교수의 한글표기 : 이건재
공동교수의 한글표기 : 이병휘
지도교수의 영문표기 : Kun-Jai Lee
공동교수의 영문표기 : Byong-Whi Lee
수록잡지명 : "Anatase-rutile transition in titania thin films prepared by MOCVD". Materials research bulletin. Elsevier Science Ltd., 32, pp. 431-440 (1997)
학위논문 학위논문(박사) - 한국과학기술원 : 원자력공학과,
서지주기 참고문헌 : p. 101-106
주제 티타늄산화막
금속유기화학기상증착
운반기체
낮은 온도
분역벽
$PbTiO_3$
MOCVD
Carrier Gas
Low temperature
Domain wall
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