高性能氧化鎳薄膜製程開發

大部分的透明導電膜，如氧化銦錫和氧化鋅皆為n型傳導方式，因此若要製備p-n接面的光電元件，開發p型半導體氧化物薄膜之鍍製技術即是一個重要的課題。通常化學計量比氧化鎳的電阻率極高，約為1013 Ω•cm。而氧化鎳薄膜的電洞主要來自Ni空位，可藉助製程參數調控或摻雜一價元素來提升薄膜的p型導電性，因此氧化鎳極具製備成p型導電膜的潛力。本研究第一部分採用傳統磁控濺鍍技術鍍製氧化鎳薄膜於康寧1737 F玻璃基板上。並藉由金屬元素(Ag、Cu及In)添加來促進p型氧化鎳薄膜的光電性質。實驗結果顯示，當NiO-Ag複合膜中之Ag含量低於4.2 at.%時，薄膜會呈現p型傳導；然而Ag含量超過9.3 at.%後，薄膜中過量的Ag原子會析出於晶界，致NiO-Ag複合薄膜轉變成n型傳導。再者，當薄膜中之Cu含量達9.18 at.%以上時，NiO-Cu複合薄膜皆呈現p型傳導方式，這可歸因於大量的Ni2+晶格位置被Cu+離子所取代，因此高含量Cu摻雜會導致NiO薄膜之結晶性顯著下降。此外，透過添加15.6 at.%以上之In可製備出n型導電NiO薄膜，且In摻雜有助於提高NiO薄膜的熱穩定性。緊接著，我們發現在純氧的氛圍下藉助Ar離子轟擊可進一步改善p型NiO-Ag複合薄膜的導電性。本研究第二部分採用新穎高功率脈衝磁控濺鍍(HIPIMS)系統在氬、氧各為50 %的氛圍下，調變工作週期以反應性濺鍍方式沈積p型NiO薄膜於康寧1737 F玻璃基板上。XRD分析顯示，在較低工作週期(即較高的靶尖峰功率密度)下鍍製之NiO薄膜傾向(200)織構，且其晶粒也較微細。我們也發現降低工作週期有助於提升濺鍍Ni原子離化率，致使NiO薄膜中產生較多的Ni2+空位，因而可提升電洞載子濃度，然而載子遷移率及薄膜穿透率會降低。

關鍵字

傳統磁控濺鍍； NiO薄膜； NiO-Ag薄膜； NiO-Cu薄膜； NiO-In薄膜； Ar離子轟擊；新穎高功率脈衝磁控濺鍍；光電性質

並列摘要

Most oxide semiconductors such as indium tin oxide, zinc oxide, etc. show n-type conduction. Hence, in p–n junction devices, synthesizing a p-type oxide-based semiconductor is an important issue. Nickel oxide (NiO) is a candidate for p-type transparent conducting oxide (TCO) materials because hole transport originates from nickel vacancies. Generally, the stoichiometric NiO is an insulator with a high electrical resistivity of 1013 Ω•cm. However, its conductivity can be enhanced significantly by adjusting certain process parameters and adding monovalent atoms. In the first part, the conventional magnetron sputtering technique was employed to deposit the NiO thin films onto Corning 1737F glass substrates. The optoelectronic properties of NiO films can be enhanced by doping metal elements such as Ag, Cu and In in the films. The results show that the NiO–Ag composite film with Ag content of 4.2 at.% shows p-type conduction. However, it becomes n-type when the Ag content increases to 9.3 at.%, which results from the Ag atoms segregating at grain boundaries in the presence of excess Ag atoms in NiO films. Furthermore, all NiO–Cu films show p-type conduction when the Cu content increases to above 9.18 at.%. Large amounts of Ni2+ ions in a NiO crystallite are replaced by the Cu+ ions, leading to p-type conduction and the degradation of crystallinity in NiO–Cu composite films that have a higher Cu content. On the other hand, semi-transparent conductive NiO-In films with n-type conduction can be achieved by the addition of indium of more than 15.6 at.%. The thermal stability of NiO films can be improved by adding higher indium content in the films. Finally, it is found that the electrical properties of p-type NiO-Ag films are further improved by Ar ion bombardment in an oxygen atmosphere. In the second part, the NiO films were deposited onto Corning 1737F glass substrates using high power impulse magnetron sputtering (HIPIMS) in 50 % Ar + 50 % O2 atmospheres with various duty cycles. The XRD patterns show that the NiO films with fine grains and (200) texture are obtained when the films are deposited at lower duty cycles (higher peak power densities). In addition, the ionization rate of Ni atoms in the sputtering process increases upon decreasing the duty cycle, resulting in the formation of more vacancies at Ni2+ sites and an increase of hole concentrations in the NiO films. However, both the carrier mobility and transmittance of the films drop.

並列關鍵字

Conventional magnetron sputtering ； NiO films ； NiO–Ag films ； NiO–Cu films ； NiO–In films ； Ar ion bombardment ； Novel high power impulse magnetron sputtering ； Optoelectronic properties

參考文獻

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高性能氧化鎳薄膜製程開發

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