以陽極氧化法於鈦塊材與鍍鈦矽晶片上製備奈米二氧化鈦薄膜之研究

Abstract

摘 要 本研究主要為鍍鈦矽晶片與鈦塊材於1 M KOH中以掃描電壓、掃描電流、定電壓與定電流模式之陽極氧化法製備奈米二氧化鈦薄膜，並探討其微結構、結晶相及陽極氧化膜生成速率。 在掃描電壓模式下，鈦膜以掃描速率3~25 mV/s生成氧化膜為奈米網狀結構，生成的的最低電壓為5 V，當電壓超過27 V時氧化膜開始出現裂縫，而在較高的掃描電壓速率下如500 mV/s則無奈米網狀結構之氧化膜生成，另外，鈦塊材以掃描速率10 mV/s，生成奈米網狀結構之最低電壓為6 V，在電壓超過30 V時開始出現裂縫，電壓值皆較鈦膜者為高。而經由拉曼光譜分析氧化膜得知，鈦膜於截止電壓為8 ~27 V生成brookite TiO2及anatase TiO2混合相，截止電壓為27 V以上則為單一anatase TiO2結晶相，而鈦塊材於截止電壓13~32 V生成brookite TiO2, Ti2O3及anatase TiO2混合相，截止電壓32 V以上為單一anatase TiO2結晶相，其電壓值皆較鈦膜者為高。 在掃描電流模式下，鈦膜以掃描速率0.001 m~0.003 mA/s，生成奈米網狀結構氧化膜的最低電流3 mA，而當電流超過15 mA時開始出現裂縫；另外，鈦塊材以掃描速率0.003 mA/s，生成奈米網狀結構的最低電流為8mA，在電流超過20 mA時開始出現裂縫，電流值皆較鈦膜者為高。經由拉曼光譜分析氧化膜得知，於截止電流4~13 mA生成brookiteTiO2, Ti2O3及anatase TiO2混合相，截止電流15 mA以上為單一anatase TiO2結晶相。 鈦膜於定電壓模式，電壓為5 V及10 V生成奈米網狀結構之氧化膜，在較高的電壓20 V則為奈米孔洞結構，拉曼光譜分析得知電壓10 V氧化10~60分鐘為brookiteTiO2，電壓5V氧化60與70分鐘為Ti2O3及brookite TiO2混合的結晶相。在定電流模式下，電流為3 mA以下為奈米網狀結構，3~5 mA為極微小的孔洞生成，5 mA以上則為奈米孔洞結構，拉曼光譜分析得知電流3與10 mA為Ti2O3及brookite TiO2混合的結晶相。中間相brookite TiO2 及Ti2O3皆會隨著氧化時間的增加而有訊號強度減弱的趨勢，此為中間相逐漸相變為單一 anatase TiO2所導致。 將掃描電壓與掃描電流模式中不同截止電壓及截止電流，以及定電壓與定電流模式中不同氧化時間之實驗條件下之微結構和結晶相結果整理分析成陽極氧化生成條件之動力學相圖，此圖主要可幫助我們預測在不同陽極氧化製程參數下，氧化膜之微結構和結晶相。 而在定電流模式下由電壓對時間關係圖，有一文獻末曾提及之特別現象，即鈦膜與鈦塊材之電壓值皆有振盪現象，其中鈦膜的振盪現象較為密集，推測為其在氧化過程中會有氧化膜溶解生成微小裂縫，因而造成其氧化成長速率較鈦塊材快。而由一半鍍鈦膜的鈦塊材上以陽極氧化法之定電壓模式，發現相較於鈦膜區所生成之奈米網狀結構之二氧化鈦薄膜，鈦塊材區僅有微量之奈米絲狀二氧化鈦，因而證實了鈦膜之成長速率快於鈦塊材。 至於，在微影製程之圖形化(patterning)之鍍鈦膜矽晶片上以陽極氧化法之掃描電壓模式，成功地製備出緻密的奈米網狀結構之二氧化鈦薄膜。因此，相較於鈦塊材鍍鈦膜矽晶片可應用於元件。

Abstract TiO2 nano-structured thin films, prepared via anodic oxidation method, were discussed in this study. These films were prepared on high pure bulk Ti and Ti film substrates in 1M KOH alkaline electrolytes and thereby the nano-structured, crystalline phase and anodic growing rate were demonstrated. The FE-SEM results show that nano-network structured TiO2 films were fabricated on Ti coated Si wafer substrates via potentiodynamic mode with a scanning cutoff voltage ranging 5~40 V by different scanning rate 3~25 mV/s in 1M KOH. Raman results revealed that the crystalline phase of Ti film with a scanning cutoff voltage ranging 8~27 V are brookite TiO2 and anatase TiO2 mixed phase, however, scanning cutoff voltage over 27 V are single anatase TiO2, moreover, the cutoff voltage for bulk Ti ranging 13~32 V are brookite TiO2, Ti2O3 and anatase TiO2 mixed phase, while the cutoff voltage above 32 V are single anatase TiO2 phase, which shows higher voltage than that of Ti film substrate. On the other hand, galvanodynamic mode of Ti film substrates using scanning rate ranging 0.001~0.003 mA/s showed the lowest parameter 3 mA for the fabrication of nano-network structured oxide film, while the bulk Ti substrates using scanning rate 0.003 mA/s, the lowest parameter to fabricate nano-network structured oxide film is 8 mA, which revealed a higher than Ti film substrates. The crystalline phase of the oxide film for the cutoff current ranging 4~13 mA are brookite TiO2, Ti2O3 and anatase TiO2 mixed phase, while that above 15 mA are single anatase TiO2 phase. The oxidation dynamic phase diagram utilizing different parameters of potentiodynamic, galvanodynamic, potentiostatic and galvanostatic mode are illustrated. These oxidation dynamic phase diagram availed us to understand the formation of the crystalline phase or nano-structured by what kind of mode in studied. Furthermore, the oxide nano-network structured TiO2 thin film is successfully growth on the patterning Ti/Si film by potentiodynamic mode of anodic oxidation method, this application can be used in the electronic devices that can't be fabricated by the bulk Ti substrate.