研究生: |
江國慶 K.C.Jiang |
---|---|
論文名稱: |
鍍膜參數對雷射鍍鈦酸鍶鋇薄膜特性的影響 Influence of Deposition Parameters on Characteristics of Laser |
指導教授: |
鄭秀鳳
Cheng, Hsiu-Fung |
學位類別: |
碩士 Master |
系所名稱: |
物理學系 Department of Physics |
畢業學年度: | 81 |
語文別: | 中文 |
論文頁數: | 77 |
中文關鍵詞: | 薄膜;鈦酸鍶鋇;脈衝雷射鍍 、Films;Strontium Barium Titanate;Pulsed Laser Deposition |
論文種類: | 學術論文 |
相關次數: | 點閱:170 下載:0 |
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本論文主要是用雷射法鍍鈦酸鍶鋇薄膜,探討鍍膜參數對薄膜晶相、微觀
結構和電性的影響。鍍膜參數之基板溫度和氧壓均會對薄膜特性有較大的
影響,在低基板溫度所鍍之膜均為非晶形。薄膜在矽(Si)基板溫度
500℃以上可有鈣鈦礦結晶相,白金/矽 Pt/Si)基板則在450℃以上,
可出現鈣鈦礦結晶相,此乃因白金 Pt)與鈦酸鍶鋇的晶格配合性較佳,
故在較低的基板溫度便可長出薄膜具有鈣鈦礦的結晶相。雷射能量密度有
個臨界值,在 1.6 J/c㎡以上才有結晶相。在高溫真空下易形成鈦酸鍶鋇
薄膜(110)與(111) 之結晶優向性。薄膜鍍在Si基板之金屬─氧化物
─半導體(MOS)結構與鍍在Pt/Si基板之金屬─絕緣物─金屬(MIM)結
構中,由於MOS中SiO2與薄膜的電容串聯效應,所以降低了 MOS的電容值
,一般在相同條件下,MIM具有較高的電容值與介電常數。介電常數在MOS
結構為 10~149,在MIM結構為 44~460,最佳之電荷儲存密度Qc值
為3.65 μC/c㎡。鈦酸鍶鋇薄膜能隙值Eg~2.84 eV。
The laser ablation technique has been applied to synthesize the
(Sr,Ba)TiO3 thin films. The influence of depositing parameters
on the crystal structure, microstructure and the electrical
properties of the films has been systematically examined. Among
the important depositing parameters, the substrate temperature
and chamber oxygen pressure affect the characteristics of the
films most prominently. The films are of amorphous structure
when deposited at low substrate temperature. The crystalline
phase of the (Sr,Ba)TiO3 films on Si-substrates can be obtained
only when the substrate temperature is higher than 500℃. But
the perovskite phase has already formed at 450℃ substrate
temperature, when ablated on Pt-coated Si. The critical laser
fluence necessary to result in stoichiometric and good
crystalline films is 1.6 J/c㎡. Low depositing oxygen pressure
in conjunction with high substrate temperature facilitate the
formation of highly textured (Sr,Ba)TiO3 films with (110) and
(111) preferred orientation. The metal-oxide-semiconductor
(MOS) structure of the (Sr,Ba) TiO3 films deposited on Si-
substrates exhibits significantly lower electric capacitance
than that of the metal-insulator- metal (MIM) structure of
those films deposited on Pt-coated Si-substrates. It is
ascribed to the formation of SiO2 layer which is seriesly
connected to the (Sr,Ba)TiO3 film in the former case. The
dielectric constant is 10~149 and 44~460, respectively, for
MOS and MIM structure, the best storage charge density obtained
is Qc=3.65 μC/c㎡. The value of energy gap of the (Sr,Ba)TiO3
thin film is Eg~2.84 eV.
The laser ablation technique has been applied to synthesize the