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Preparation of titanium thin films by physical vapor deposition using air/Ar mixtures and applications of the films in electromagnetic interference shielding
|關鍵字:||PVD;物理氣相沉積法;Titanium;electromagnetic interference shielding;鈦;電磁波干擾屏蔽||出版社:||材料科學與工程學系所||摘要:||
鈦金屬薄膜具有良好的電性、熱性質及抗腐蝕等優點，同時也具有優異的生物相容性，因此被廣泛的運用在在各工業領域上。然而過去文獻在利用物理氣相沉積法製備鈦金屬薄膜時，皆須耗費大量的時間將背景壓力抽至高真空，並在高真空環境下通入高純度的濺鍍氣體Ar進行鈦薄膜之鍍著。本研究主要在低真空環境下 (1.3×10-2 Pa) 通入air/Ar之混和氣體製備鈦金屬薄膜，如此可以節省抽真空之時間並能達到降低製程成本及製程時間之目標。
本研究利用物理氣相沉積法，在背景壓力為1.3×10-2 Pa下，固定鍍著功率300 W，鍍著時間10分鐘，而工作壓力範圍則在0.187~0.192 Pa之間，控制air/Ar流量比值為(1~6)/100之間，並將所鍍著之薄膜利用X光繞射儀 (XRD) 分析其薄膜結晶相，再分別利用場發射電子顯微鏡 (FE-SEM) 以及原子力顯微鏡 (AFM) 分析薄膜之微結構以及表面形貌，而薄膜之成分組成則是利用場發射微探分析儀 (FE-EPMA) 以及X光光電能譜儀 (XPS) 分析，接著利用四點探針分析薄膜之電阻率以及利用奈米壓痕儀分析其機械性質。而XRD分析薄膜之結晶相為Ti的六方晶結構，且晶粒尺寸則隨著air/Ar比值增加有減小的趨勢；薄膜電阻率介於156~200 µΩ-cm之間；而薄膜硬度則在14.5~26 GPa之間；成分分析之結果，N原子百分比則在1.6~17.5 at.%，O原子百分比約為5~6 at.%，與文獻中Ti薄膜之性質比對後，證實所鍍著之薄膜為Ti薄膜。且Ti薄膜之電阻率及硬度會隨著薄膜中的N原子百分比增加而上升。然而在本研究中發現，增加基板偏壓時，薄膜中的N原子百分比會隨之下降，此時薄膜電阻率以及硬度也因為N原子百分比減少而降低。
在電磁波屏蔽效應的應用方面，將本研究所鍍著之Ti薄膜進行電磁波屏蔽效益值 (EMSE) 的量測，量測的電磁波頻率範圍在300 MHz~5000MHz之間，結果顯示皆具有平均值的屏蔽能力，可以屏蔽掉99.9%以上之電磁波，並發現當薄膜電阻率越低其電磁波屏蔽能力越好。一般以金屬薄膜做為電磁波屏蔽材料皆須鍍上抗腐蝕層以及緩衝層，以保護金屬薄膜。然而本實驗中在高背景壓力(1.3×10-2 Pa)下所鍍著之Ti薄膜具有良好的電性，同時具較高的硬度值，因此可以改善純Ti薄膜硬度較低之缺點，且Ti薄膜本身即具備優異的抗腐蝕能力，因此本研究中，所鍍著之Ti薄膜適合做為電磁波屏蔽材料，並且可省去鍍著抗腐蝕層以及緩衝層之成本。
Owing to their low electrical resistivity, high thermal stability and corrosion resistance, as well as excellent biocompatibility, titanium thin films have been widely applied in the industry. It is known that preparing titanium thin films by physical vapor deposition usually takes a lot of time to achieve the vacuum eviroment. Argon was used as the sputtering gas. In this study, air/Ar mixed gases were employed to prepare Ti thin films to low vacuum environment (1.3×10-2 Pa). Thus, the processing cost and time can be reduce substantially.
In this study, Ti thin films were deposited by dc magnetron sputtering under the base pressure of 1.3×10-2 Pa and the working pressure of 0.187~0.192 Pa. The dc power supply was fixed at 300 W and the deposition time was fixed at 10 min. The crystal structure of the Ti films were determined by X-ray diffraction. The microstructures and morphologies of the deposited Ti films were examined using field emission scanning electron microscopy and atomic force microscopy. The compositions of the films were obtained by field emission electron probe X-ray micro-analysis and .The resistivity of the Ti films were measured using a four-point probe and nanoindentation was used to measure the hardness of the films. The crystal structure of the films exhibited a hcp structure, and the grain size decreased with increasing air/Ar flow ratio; the resistivity of the films ranged from 156 to 200 µΩ-cm, the hardness was about 14.5~26 GPa, and the nitrogen content was about 1.6~17.5 at.%, the oxygen content was about 5~6 at.%. Compared with the data reported in the literature, it has been confirmed that air/Ar mixtures could be used to prepare Ti films. Furthermore, the nitrogen content of the films decreased with increasing the substrate bias and the decrease of resistivity and hardness was mainly due to the decrease of the nitrogen content.
As for the measurement of electromagnetic interference shielding effectiveness (EMSE), the results show an average shielding ability. Based on the results of the EMSE, the shielding ability is inversely proportional to the resistivity of the films. In general, the metal films are used as electromagnetic shielding materials to be sputtered with anticorrosion-layer and buffer layer to protect the metal films. However, Ti thin films which were sputtered in the low vacuum environment (1.3×10-2 Pa)have good electrical properties and hardness, it can improve the hardness of pure Ti thin films of the shortcomings of the lower. Ti thin films have excellent corrosion resistance, so this study of the Ti-plated as a thin film for electromagnetic shielding materials, and can save the cost of anticorrosion layer and buffer layer.
|Appears in Collections:||材料科學與工程學系|
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