Browsing by Author "Jan, Chueh-Kuei"

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Characteristics of low-temperature pulse-laser-deposited (Pb,Sr)TiO3 films in metal/ferroelectric/silicon structure
(2007-01-07)
Wang, Jyh-Liang
;
Lai, Yi-Sheng
;
Lee, Trent Gwo-Yann
;
Chiou, Bi-Shiou
;
Tsai, Chun-Chien
In this study, pulsed- laser deposited ( Pb, Sr) TiO3 ( PSrT) films on p- type Si were studied at low substrate temperatures ranging from 300 to 450 degrees C for metal/ ferroelectric/ semiconductor applications. The substrate temperature strongly enhances film crystallinity without significant inter- diffusion at the PSrT/ Si interface and affects the electrical properties. As the substrate temperature increases, the films have smaller leakage currents, fewer trap states at the electrode interfaces, clockwise capacitance versus applied field hysteresis loops and larger memory windows correlated with superior crystallinity. Conversely, 300 degrees C- deposited films exhibit a small and counterclockwise loop with a positive shift of the flatband voltage, attributed to more negative trap charges within the films. However, the high substrate temperature ( 450 degrees C) may produce serious Pb - O volatilization, incurring more defects and leakage degradation. The analyses of fixed charge density and flatband voltage shift reveal the trap status and agree well with the leakage characteristic. An electron band model of the Pt/ PSrT/ Si electronic structure is proposed to explain the electrical behaviour. The excellent fatigue endurance with a small variation of memory windows (< 11%) after 1010 switching is also demonstrated.
Structural and electrical investigation of laser annealed (Pb,Sr)TiO3 thin films
(2008-01-01)
Wang, Jyh-Liang
;
Lai, Yi-Sheng
;
Liou, Sz-Chian
;
Chiou, Bi-Shiou
;
Jan, Chueh-Kuei
Material and electrical characteristics of (Pb,Sr)TiO3 (PSrT) films irradiated by various laser pulses and laser fluences are investigated in this work. Enhanced crystallinity can be obtained after excimer laser annealing (ELA). However, grain growth induced by ELA is nonuniform, and the effect is limited to the upper region of the films. As the number of laser pulses increases to 120, the film shows stronger diffraction intensities and increased oxygen content, resulting in a distinct capacitance versus electric field hysteresis loop and a larger dielectric constant than the nonirradiated one. The leakage current is found to be associated with the interface quality. The conduction mechanism of nonirradiated and irradiated PSrT films is mainly governed by Schottky emission at low electric fields, whereas the Poole-Frenkel emission occurs for films irradiated with more than 120 laser pulses or laser fluences larger than 90.5 mJ/cm(2) at high electric fields. (C) 2008 American Vacuum Society.
Structural and electrical investigations of pulse-laser-deposited (Pb,Sr)TiO3 films at various oxygen partial pressures
(2007)
Wang, Jyh-Liang
;
Lai, Yi-Sheng
;
Liou, Sz-Chian
;
Chou, Chen-Chia
;
Tsai, Chun-Chien
Pulsed-laser deposited (Pb,Sr)TiO3 (PSrT) films on Pt/SiO2/Si substrate deposited at various oxygen partial pressures (P-O2), ranging from 50 to 200 mTorr, were investigated in this work. PSrT films exhibit (100) preferred orientation at lower P-O2 and then transit to (110) preferred orientation above 100 mTorr. The paraelectricity/ferroelectricity transition and dielectric constant of PSrT films are associated with the preferred orientation and oxygen concentration at various P-O2. Furthermore, films deposited at higher P-O2 exhibit higher breakdown field and smaller leakage current density as a consequence of fewer oxygen vacancies. Except for the case of films deposited at 200 mTorr, the conduction mechanism is identified as Schottky emission/Poole-Frenkel emission at low/high electric fields. (c) 2007 The Electrochemical Society.
Study on fatigue and breakdown properties of Pt/(Pb,Sr)TiO3/Pt capacitors
(2006-11-22)
Wang, Jyh-Liang
;
Lai, Yi-Sheng
;
Chiou, Bi-Shiou
;
Tseng, Huai-Yuan
;
Tsai, Chun-Chien
Pulsed- laser deposited ( Pb, Sr) TiO3 ( PSrT) films on Pt/ SiO2/ Si substrate at various ambient oxygen pressures ( P-O2) are investigated in this work. Films deposited at P-O2 below 100 mTorr exhibit the ( 100) preferred orientation and a tetragonal structure with larger tetragonality. In addition, films deposited at 80 mTorr exhibit the most apparent ferroelectric properties in contrast to those deposited at 200 mTorr. Moreover, films deposited at higher P-O2 also exhibit longer lifetimes and higher breakdown fields due to their smaller leakage current density, in terms of the reduction of defects, compensation of oxygen vacancies (OVs), an improved interface and small cluster sizes. An energy band model reveals that fatigue properties of PSrT films are dominated by interfacial states at low P-O2 and by deep trapping states at high P-O2, which could be ascribed to OVs located at the interfaces and inside films, respectively.
Temperature-dependent characteristics of pulse-laser-deposited (Pb,Sr)TiO3 films at low temperatures
(2008-01-01)
Wang, Jyh-Liang
;
Lai, Yi-Sheng
;
Chiou, Bi-Shiou
;
Chou, Chen-Chia
;
Lee, Trent Gwo-Yann
Pulsed laser deposition (PLD) of (Pb,Sr)TiO3 (PSrT) film on Pt/SiO2/Si at low substrate temperatures (T-s), ranging from 300-450 degrees C, has been investigated. As T-s increases, the films reveal coarsening clusters, improved crystallization of the perovskite phase, distinct capacitance-electric field (C-E) hysteretic loops and a larger dielectric constant. The 350 degrees C-deposited film shows strong (100) preferred orientation and optimum dielectric properties with the dielectric constant of similar to 620. The current density increases as the measurement temperature and the electric field increase. Moreover, PSrT films exhibit a strong negative temperature coefficient of resistance (NTCR) behavior at temperatures ranging from 100 to 390 degrees C.