以快速脈衝雷射成長銦錫氧化物在M面與R面氧化鋁基板的結構與電性探討

Abstract

以快速脈衝雷射蒸鍍法(fast plused laser deposition,FPLD)成長銦錫氧化物(Indium tin oxide, ITO)薄膜在M-plane(100)和R-plane(012)的氧化鋁(sapphire)基板上。在本研究中，鍍膜時控制背景氧壓(PO2)在5x10-3~5x10-5 torr，同時，基板溫度(Ts)在750oC~500oC之間。 以x光粉末繞、高解析光源、φ掃描分析ITO薄膜結構，發現其偏好方向強烈地決定於成長條件。 在高溫高壓下，單晶(110)ITO成功地成長在M面與R面的氧化鋁基板上。反之，在低溫或低壓的環境下，晶格方向呈現多晶序包含(111)與(100)。 在φ掃描中，二重對稱的{662}ITO平行{110}M-plane氧化鋁基板，說明交界面關係為：「ITO[001]//Al2O3[020]和ITO[1-10]// Al2O3[001]」。另一方面，對R-plane氧化鋁基板而言，{662}ITO同時出現在{125}Al2O3兩邊各夾約47o，說明交界面關係為：「ITO[001]//Al2O3[9/4,3/2,-3/4]、ITO[1-10]//Al2O3[-1,2,-1]」或「ITO[001]// Al2O3[-3/4,-3/2,3/4]、ITO[1-10]// Al2O3[3,2,-1]」。 以霍爾效應與Van der Pauw四點量測技術測量ITO薄膜電性。所有的樣品皆為低電阻率在10-4 (Ωcm)數量級、載子濃度約為1020 (cm-3)數量級，而遷移率範圍在60到100 (cm2/Vs)之間

Indium tin oxide (ITO) thin films have been deposited using fast plused laser deposition (FPLD) on M-plane(100) and R-plane(012) sapphire under identical conditions. The oxygen pressure (PO2) was varied from 5x10-3 torr to 5x10-5 torr while the substrate temperature (Ts) from 700oC to 500oC for the growth conditions used in this study. The structural property of ITO films was analyzed by X-ray powder diffraction, high resolution rocking curve and φ-scan. It has been found that the preferred orientation of these films strongly depends on the growth conditions. At high substrate temperature and high oxygen pressure, single-crystalline (110)ITO were grown on M-plane and R-plane sapphire substrates successfully. Otherwise, poly-crystalline ITO including (111) and (100) appeared at low substrate temperature or low oxygen pressure. In φ-scan measurement, the two-fold {662}ITO coincide with the {110}of M-plane substrate, indicating an in-plane epitaxial relationship: ITO[001]//Al2O3[020] and ITO[1-10]// Al2O3[001]. On the other hand, for the R-plane substrate, the {662}ITO appears on both side of {125}Al2O3 by ~47o, indicating an in-plane epitaxial relationship: ITO[001]//Al2O3[2,1,-1/2] 、ITO[1-10]//Al2O3[-4/3,4/3,-2/3] or ITO[001]//Al2O3[1,-1,1/2]、ITO[1-10]//Al2O3[8/3,4/3,-2/3]. The electrical property was measured by the Hall effect and four-point probe technique. All of the samples have low electrical resistivity on the order of 10-4 (Ωcm), high carrier concentration of about 1020 (cm-3), and mobility ranging from 60 to 100 (cm2/Vs).