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TFA-MOD方法制备YBCO超导薄膜研究   总被引:4,自引:1,他引:3  
采用TFA-MOD方法在LaAlO3(001)单晶基片上制备了性能良好的YBCO超导薄膜:临界电流密度(Jc)可达3MA/cm2(77K,0T),超导转变温度Tc≈90K,转变宽度ΔTc=0.5K,其一次涂层厚度达338nm.通过X射线衍射(XRD)分析表明YBCO具有纯c-轴取向、无a-轴取向的晶粒存在.ω扫描分析表明该YBCO薄膜具有很好的面外外延性,其摇摆曲线的半高宽(FWHM)为0.653°. 用SEM分析也表明膜的表面无裂纹存在,表面平整,没有a轴晶粒生长.  相似文献   
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<正>Sodium beta-alumina(SBA) is deposited on AlGaN/GaN by using a co-deposition process with sodium and Al2O3 as the precursors.The X-ray diffraction(XRD) spectrum reveals that the deposited thin film is amorphous.The binding energy and composition of the deposited thin film,obtained from the X-ray photoelectron spectroscopy(XPS) measurement,are consistent with those of SBA.The dielectric constant of the SBA thin film is about 50.Each of the capacitance-voltage characteristics obtained at five different frequencies shows a high-quality interface between SBA and AlGaN.The interface trap density of metal-insulator-semiconductor high-electron-mobility transistor(MISHEMT) is measured to be(3.5~9.5)×1010 cm-2·eV-1 by the conductance method.The fixed charge density of SBA dielectric is on the order of 2.7×1012 cm-2.Compared with the AlGaN/GaN metal-semiconductor heterostructure high-electronmobility transistor(MESHEMT),the AlGaN/GaN MISHEMT usually has a threshold voltage that shifts negatively. However,the threshold voltage of the AlGaN/GaN MISHEMT using SBA as the gate dielectric shifts positively from—5.5 V to—3.5 V.From XPS results,the surface valence-band maximum(VBM-EF) of AlGaN is found to decrease from 2.56 eV to 2.25 eV after the SBA thin film deposition.The possible reasons why the threshold voltage of AlGaN/GaN MISHEMT with the SBA gate dielectric shifts positively are the influence of SBA on surface valence-band maximum (VBM-EF),the reduction of interface traps and the effects of sodium ions,and/or the fixed charges in SBA on the two-dimensional electron gas(2DEG).  相似文献   
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