以反應性濺鍍成長P型氧化亞銅薄膜之特性研究

The properties of p-type cuprous oxide films prepared by reactive sputtering

吳尚軒(Shang-Hsuan Wu)

指導教授 ： 林天財

共同指導教授 ： 張慎周(Shang-Chou Chang)

崑山科技大學/工程學院/電機工程研究所/碩士(2008年)

https://doi.org/10.6828/KSU.2008.00018

摘要

本研究以射頻磁控濺鍍系統，使用銅靶改變不同射頻功率及氧氣流量進行反應性濺鍍，藉以得到不同性質之氧化亞銅薄膜。此外，也在基板外加直流偏壓，探討基板偏壓對薄膜成長特性之影響。並以n-TCO/p-Cu2O結構研究不同n-TCO對太陽電池元件特性之影響。實驗以α-step量測鍍膜厚度、四點探針及霍爾量測儀量測鍍膜電阻率、X-ray繞射進行薄膜結構分析、SEM及AFM觀察其表面形貌、UV-VIS 量測光穿透率、I-V量測其開路電壓和短路電流。
實驗結果顯示，純相的氧化亞銅成長條件不易控制。氧化亞銅薄膜結晶結構、表面形貌、及光電特性與射頻功率以及氧氣流量有密切的關係。氧氣流量0.7sccm~0.9sccm，射頻功率在120W~140W時，皆可以得到純Cu2O相。而射頻功率130W，氧氣流率0.7sccm時，有最佳光電特性的，其電阻率為50.6Ω-cm，在可見光平均反射率為14%。外加基板偏壓會改變薄膜成長機制，在結晶方向（200）會隨著基板偏壓不同，表面形態也受基板偏壓機制影響，隨著偏壓增至200V粗糙度RMS由24.6nm降至13.4nm。而電性則在基板偏壓200V時，會有最低電阻率7.5Ω-cm，可見光平均光反射率則為14%。另外，高載子濃度p+-Cu2O所製作出的太陽電池元件，可能因為空乏區較窄，影響光電流之產生。

關鍵字

氧化亞銅 ； 偏壓濺鍍 ； 薄膜

並列摘要

Cuprous oxide (Cu2O) is a direct-gap semiconductor and has a very high absorption coefficient in visible light region. Transparent conducting oxides (TCO) film appling in solar cells to product semitranslucent glass, have some beneficial heat insulation and electronic generation layers. Cuprous oxide (Cu2O) is a direct bend gap and is p-type semiconductor at without doping. To understand Cu2O characteristics can provide useful and foundamental datum to promote the efficiency of solar cells.
In this study, we concentrated on the effect of deposition conditions of Cu2O film grown by reactive rf-magnetron sputtering, Cu was used as the sputtering target. The RF power and the O2 flow rate was changed in order to obtain a cuprous oxide film with different characteristics. In addition, the influence of film growing characteristics depended on bias voltage was discussed. Based on n-TCO/p-Cu2O structure, the different n-TCO materials was used to study the influence of solar cell properties. An α-step equipment was used to detect film thicknesses. A 4-points probe was used to measure a sheet resistivity and the Hall measurement was used to detect the carrier concentration and mobility. The structure could be characterized by X-ray diffraction (XRD).The surface morphologies were observed by SEM and AFM. The transmittance was measured by UV-VIS spectrophotometer. I-V measurement was used to analyzed the opens-circuit voltage and short-circuit current.
According to experimental results knew that to growing a single phases of Cu2O films was not easy to handle. The crystal surface, superficial morphologies and photoelectronic properties of cuprous oxide film were close relationship with RF power and oxygen flow rate. The oxygen flow rate was varied from0.7sccm to 0.9sccm and the rf power was changed from 120W~140W. A single phase of Cu2O films can be obtained. At RF power of 130W and oxygen flow rate of 0.7sccm, the best photoelectronic properties, which resistivity is 50.6Ω-cm and average reflection is 14% in visible light, were obtained. The preferred orientation of (200) and surface morphologies were significantly changed depending on bias voltages, therefore, the results showed the growth mechanism was also closely relative to bias voltages. When the bias voltage increased from zero to 200V, the roughness in rms value fell from 24.6nm to 13.4nm. The lowest resistivity of 7.5Ω-cm in our experiments was gotten at the substrate bias of 200V, and average reflection was 14% in visible light region at this condition. Due to high carrier concentration in p+-Cu2O layers, the depletion region at P/N junction is very narrow which will be influence photoelectric current. Therefore, the photoelectric current can not be detected, in our experiments.

並列關鍵字

Cuprous oxide ； Bias sputtering ； Thin films

參考文獻

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