A Structural Study of Copper Oxide Grown on Cu(110) under Near Ambient Pressure Conditions

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题名:	A Structural Study of Copper Oxide Grown on Cu(110) under Near Ambient Pressure Conditions
作者:	梁銓軒;Liang, Quan-Xuan
贡献者:	物理學系
关键词:	銅(110);氧化銅;STM;APXPS;RHEED
日期:	2025-01-20
上传时间:	2025-04-09 16:58:23 (UTC+8)
出版者:	國立中央大學
摘要:	在近常壓的氧氣壓力條件下，兩種不同型態的氧化銅已經被證實。初始態的氧化銅與基板間的交互作用和隨著氣壓上升造成的結構變化都會影響其催化能力。隨著由高真空至近常壓的氧氣壓力變化並控制在合適的成長溫度 (550K)，藉由高能電子繞射 (RHEED)、掃描穿隧顯微鏡 (STM) 及常壓 X-ray 光電子能譜 (AP-XPS) 去觀察晶體結構和電子態的變化在銅(110) 表面。在氧氣氣壓小於 10−5 托時，電子繞射結果顯示表面由 c(6 × 2) 和 (2 × 1) 共存態組成。隨著氧氣壓力處於 10−5 托至 10−2 托之間且曝氧量大於 1.8 × 104L，由繞射結果我們發現表面始終只有 c(6 × 2) 的結構出現，銅 2p 圖譜只表現出塊材的訊號也表明沒有氧化銅的形成。然而，氧 1s 圖譜顯示氧量的確上升。此外，在 STM 圖裡面，我們發現到平台上的高低起伏出現明顯的改變，從而推斷表面下有氧與銅形成鍵結導致此現象。當氧氣壓介於 10−2 托至 10−1 托之間，氧化亞銅逐漸佔據表面。而在初始階段時，氧化亞銅與 c(6 × 2) 共存時為雙重態且偏好向下生長。最終在 10−1托的氣壓下，氧化亞銅的厚度大約是 3.5 奈米且結構改變成非晶態，還伴隨著氧化銅的薄膜態。隨著增加氧氣壓力至大於 1 托時，由光譜我們可得知氧化銅厚度超過 3.41 奈米且強化學吸附的氧明顯增加。然而，在此氣壓下無法觀察到繞射結構，表示氧化銅的成長方式轉為無定型態。氧氣氣壓進一步調節到 5 托時，沒有新的銅化物出現。氧化銅厚度也沒有明顯變化，僅有強化學吸附的氧數量上的提升。 ;Under near ambient oxygen pressure condition, there are two kinds of copper oxide having been confirmed. The interaction between initial state of copper oxide and substrate and the structure evolution with pressure increase will influence the catalytic capability. With regulating the oxygen pressure from high vacuum to near ambient pressure and controlling at moderate growth temperature (550 K), we observe the changes of crystal structure and electronic state on Cu(110) surface by reflective high energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). When the oxygen pressure is below 10−5 Torr, the result from electron diffraction demonstrates the surface is composed of the co-existence state of c(6 × 2) and (2 × 1). As the oxygen pressure is regulated in the interval between 10−5 Torr and 10−2 Torr and the oxygen exposure is greater than 1.8 × 104 L, only the structure c(6 × 2) appears on the surface from the diffraction result and only the signal of bulk copper is captured in the Cu 2p spectrum which denotes that there is not the formation of copper oxide. However, the oxygen 1s spectrum shows that the amount of oxygen does increase. In addition, we found there was a significant undulation in the terrace in the STM images, which led to the inference that this phenomenon was caused by the formation of bonds between oxygen and copper under the surface. When the oxygen pressure is in the interval between 10−2 Torr and 10−1 Torr, Cu2O gradually occupies the surface. In the initial stage, Cu2O is double phase when it coexists with c(6×2) and also prefers to grow downward. Finally, at a pressure of 10−1 Torr, the thickness of Cu2O is about 3.5 nm and the structure changes to the amorphous state, accompanied by thin film state of CuO. As the oxygen pressure is increased to greater than 1 Torr, from the spectrum we can see that the CuO thickness exceeds 3.41 nm and the strongly chemisorbed oxygen increases significantly. However, no diffraction structure can be observed at this pressure, which indicates that the growth mode of CuO transfers to the amorphous state. The oxygen pressure was further adjusted to 5 Torr, no new copper compounds appear. The thickness of CuO has not changed significantly, only the amount of strongly chemisorbed oxygen has increased.
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