Si掺杂对GaAs纳米线发光特性的影响EI北大核心CSCD

采用分子束外延技术(MBE)在Si(111)衬底上生长了非掺杂和Si掺杂砷化镓(GaAs)纳米线(NWs)。通过扫描电子显微镜(SEM)证实了生长样品的一维性;通过X射线衍射(XRD)测试和拉曼光谱(Raman)证实了掺杂GaAs纳米线中Si的存在;通过光致发光(PL)研究了非掺杂和Si掺杂GaAs纳米线的发光来源,掺杂改变了GaAs纳米线的辐射复合机制。掺杂导致非掺杂纳米线中自由激子发光峰和纤锌矿/闪锌矿(WZ/ZB)混相结构引起的缺陷发光峰消失。     

Si掺杂对GaAs纳米线发光特性的影响

采用分子束外延技术(MBE)在Si(111)衬底上生长了非掺杂和Si掺杂砷化镓(GaAs)纳米线(NWs)。通过扫描电子显微镜(SEM)证实了生长样品的一维性;通过X射线衍射(XRD)测试和拉曼光谱(Raman)证实了掺杂GaAs纳米线中Si的存在;通过光致发光(PL)研究了非掺杂和Si掺杂GaAs纳米线的发光来源,掺杂改变了GaAs纳米线的辐射复合机制。掺杂导致非掺杂纳米线中自由激子发光峰和纤锌矿/闪锌矿(WZ/ZB)混相结构引起的缺陷发光峰消失。     

MOCVD自催化法在Si(100)衬底上生长InP/InGaAs核壳结构纳米线

采用自催化法,利用金属有机化学气相沉积技术,在Si(100)衬底上成功制备了InP/InGaAs核壳结构纳米线。通过扫描电子显微镜观察纳米线形貌,在核壳结构纳米线的顶端催化剂转化成了颗粒状晶体。利用X射线衍射和透射电子显微镜研究了InP纳米线上生长InGaAs外壳的过程,并应用X射线能量色散能谱仪对纳米线顶端进行了轴向和径向的线扫描,得到了纳米线上元素组分分布。催化剂的转化发生在制备InGaAs壳之前的升温过程中,且形成的晶体中含有合金成分。InGaAs壳的组分调整可以通过改变生长过程中生长源气体的流量来实现。     

衬底对化学气相沉积法制备氧化硅纳米线的影响

通过化学气相沉积法在不同衬底上制备了大量的氧化硅纳米线.选用衬底为Si片、带有约100nm厚SiO2氧化层Si片和石英片.利用场发射扫描电子显微镜(SEM)和透射电镜(TEM，配备有能谱仪)对样品的表面形貌、结构和成分进行研究.结果表明：这些纳米线都为非晶态，但在不同衬底上生长的纳米线形貌、尺寸和化学成分不同.讨论了各种衬底对不同特征氧化硅纳米线生长的影响. 关键词： 化学气相沉积 纳米线 纳米颗粒     

气相输运法制备ZnO薄膜(英文)

运用气相输运技术在不同的衬底上制备ZnO薄膜,同时对这些ZnO薄膜的表面形貌、晶体结构和光学特性进行表征。在扫描电子显微镜图像上可以看到,相比没有镀金的Si衬底,ZnO纳米颗粒在镀金的Si衬底上的生长尺寸较大。X射线衍射测试结果表明,在Si(111)和Si(100)衬底上生长的ZnO薄膜显示出不同的六角纤锌矿结构的衍射峰,但没有出现立方闪锌矿ZnO结构的衍射峰。在镀金的Si衬底上,ZnO薄膜生长取向主要为c轴方向。此外,所有ZnO样品的光致发光谱上均只出现一个狭窄且强的紫外峰,约在389 nm(3.19 eV)波长处。     

树形结构Si/ZnO纳米线阵列的制备及光学性能

用一种低成本的方法制备出了树形结构Si/ZnO纳米线阵列。首先在室温条件下用金属辅助化学腐蚀法在Si(100)衬底上制备了Si纳米线阵列,Si纳米线的直径尺寸及分布都很均匀,通过改变腐蚀时间,能够得到高度不同的Si纳米线阵列。利用磁控溅射在Si纳米线表面制备一层ZnO薄膜,然后利用水热法在Si纳米线阵列上生长了ZnO纳米线。通过扫描电子显微镜(SEM)、能谱分析仪(EDS)和光致发光(PL)测试对样品进行了表征。通过这种方法制备的Si/ZnO复合结构在太阳能电池、光催化等领域有潜在应用价值。     

Si(110)和Si(111)衬底上制备InGaN/GaN蓝光发光二极管

分别在Si(110)和Si(111)衬底上制备了In Ga N/Ga N多量子阱结构蓝光发光二极管(LED)器件.利用高分辨X射线衍射、原子力显微镜、室温拉曼光谱和变温光致发光谱对生长的LED结构进行了结构表征.结果表明,相对于Si(111)上生长LED样品,Si(110)上生长的LED结构晶体质量较好,样品中存在较小的张应力,具有较高的内量子效率.对制备的LED芯片进行光电特性分析测试表明,两种衬底上制备的LED芯片等效串联电阻相差不大,在大电流注入下内量子效率下降较小;但是,相比于Si(111)上制备LED芯片,Si(110)上LED芯片具有较小的开启电压和更优异的发光特性.对LED器件电致发光(EL)发光峰随驱动电流的变化研究发现,由于Si(110)衬底上LED结构中阱层和垒层存在较小的应力/应变而在器件中产生较弱的量子限制斯塔克效应,致使Si(110)上LED芯片EL发光峰随驱动电流的蓝移量更小.     

微波等离子体化学气相沉积方法在Si衬底上生长SiC纳米线

应用微波等离子体化学气相沉积方法,在单晶Si(100)衬底上生长出SiC纳米线.应用扫描电子显微镜、透射电子显微镜、能量损失谱(EDS)和选区电子衍射(SAD)等方法对纳米线化学组成和结构进行了分析和表征.给出该纳米线的生长机理 关键词： 微波等离子体化学气相沉积 SiC纳米线 生长机理     

GaAs纳米线晶体结构及光学特性

采用分子束外延技术在N-型Si (111)衬底上利用自催化生长机制外延砷化镓(GaAs)纳米线,对生长的纳米线进行扫描电子显微镜测试,纳米线垂直度高,长度直径均匀度好.对纳米线进行光致发光(photoluminescence, PL)光谱测试,发现低温10 K下两个发光峰P1和P2分别位于1.493 eV和1.516 eV,推断可能是纤锌矿/闪锌矿(WZ/ZB)混相结构引起的发光以及激子复合引起的发光;随着温度升高,发现两峰出现红移,并通过Varshni公式拟合得到变温变化曲线.对纳米线进行变功率PL光谱测试,发现P1位置的峰位随功率增加而蓝移,而P2位置的峰位不变.通过拟合发现P1峰位与功率1/3次方成线性相关,判断可能是WZ/ZB混相结构引起的Ⅱ型发光;同时,对P2位置的峰位进行拟合,P2为激子复合发光.对纳米线进行拉曼光谱测试,从光谱图中发现GaAs WZ结构特有的E_2声子峰,因此证明生长出的纳米线为WZ/ZB混相结构,并通过高分辨透射电子显微镜更直观地观察到纳米线的混相结构.     

湿法刻蚀对Si基片孔点阵及ZnO外延薄膜周期形貌的影响

利用射频等离子体辅助分子束外延法,在刻有周期性孔点阵结构的Si衬底上生长了ZnO二维周期结构薄膜,系统研究了湿法化学刻蚀对孔形点阵Si(100),Si(111)基片表面形貌的影响,以及两种初底上ZnO外延薄膜的结晶质量与周期形貌的差异.X射线衍射及扫描电子显微测试结果表明：Si (111)衬底上生长出的ZnO二维周期结构薄膜具有较好的结晶质量与较好的周期性表面形貌.该研究结果为二维周期结构的制备提供了一种新颖的方法. 关键词： ZnO 分子束外延 Si 湿法刻蚀     

Critical diameters and temperature domains for MBE growth of III–V nanowires on lattice mismatched substrates

We report on the growth properties of InAs, InP and GaAs nanowires (NWs) on different lattice mismatched substrates, in particular, on Si(111), during Au‐assisted molecular beam epitaxy (MBE). We show that the critical diameter for the epitaxial growth of dislocation‐free III–V NWs decreases as the lattice mismatch increases and equals 24 nm for InAs NWs on Si(111), 39 nm for InP NWs on Si(111), 44 nm for InAs NWs on GaAs(111)B, and 110 nm for GaAs NWs on Si(111). When the diameters exceed these critical values, the NWs are dislocated or do not grow at all. The corresponding temperature domains for NW growth extend from 320 °C to 340 °C for InAs NWs on Si(111), 330 °C to 360 °C for InP NWs on Si(111), 370 °C to 420 °C for InAs NWs on GaAs(111)B and 380 °C to 540 °C for GaAs NWs on Si(111). Experimental values for critical diameters are compared to the previous findings and are discussed within the frame of a theoretical model. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Long Si nanowires with millimeter-scale length by modified thermal evaporation from Si powder

A modified thermal evaporation processing is reported to fabricate silicon nanowires starting from Si powder under normal pressure. In a temperature range of 1250–1290 °C, long single-crystal Si nanowires with an amorphous layer were grown in relative large quantity, and they had a millimeter-scale length and a uniform diameter of about 100 nm. A high-resolution transmission electron microscopy image indicated that the growing direction of the long Si nanowires is [111]. PACS 81.07.Bc     

Synthesis of epitaxial Si(100) nanowires on Si(100) substrate using vapor–liquid–solid growth in anodic aluminum oxide nanopore arrays

The synthesis of epitaxial Si nanowires with growth direction parallel to Si [100] on Si(100) substrate was demonstrated using a combination of anodic aluminum oxide (AAO) template, catalytic gold film sandwiched between the template and the Si(100) substrate and vapor-liquid-solid growth using SiH₄ as the Si source. After growing out from the AAO nanopores, most Si nanowires changed their diameter and growth direction into larger diameter and 〈111〉 direction. PACS 81.07.-b; 82.45.Cc     

Unidirectional hexagonal rare-earth disilicide nanowires on vicinal Si(100)-2×1

Rare-earth disilicide nanowires grown on vicinal Si(100) with a miscut of 2–2.5° toward the [110] azimuth at 600 °C were studied by scanning tunneling microscopy and compared with those grown on flat Si(001). In contrast to rare-earth disilicide nanowires grown on flat Si(100) surfaces, the nanowires grow unidirectionally along the [01̄1] direction of the vicinal Si(100) surface. Rare-earth disilicide nanowires form bundles composed of single nanowire units on both flat and vicinal surfaces. Yet, on the vicinal surface, the bundle width is comparable to the width of the terrace. The average nanowire length on the vicinal substrate is longer than that on the flat substrate. Scanning tunneling spectroscopy shows that the rare-earth disilicide nanowires have metallic properties. PACS 81.07.Vb; 81.16.Dn; 68.65.La; 68.37.Ef     

Nanostructure size evolution during Au-catalysed growth by carbo-thermal evaporation of well-aligned ZnO nanowires on (100)Si

We report the structural and morphological properties of well-aligned ZnO nanowires grown at 750 °C on Au-deposited and annealed (100)Si substrates using carbo-thermal evaporation. As-grown nanowires are made of wurtzite ZnO, have cylindrical shape and carry droplet-like nanoparticles (NPs) at their tips, as expected for vapour–liquid–solid (VLS) growth. Grazing incidence X-ray diffraction measurements demonstrate that the NPs are made of pure fcc Au. No secondary Au/Zn alloy phases were detected. Bragg diffraction patterns confirmed that the nanowires were grown with their crystal c-axes parallel to the [100] direction of Si (i.e. normal to the substrate surface), while Au NPs are mostly (111)-oriented. The diameter distribution of ZnO nanowires mimics that of the Au NPs at their tips. A quantitative study of the nanostructure size distribution after sequential annealing and growth steps evidences the occurrence of three nanoscale processes: (i) Ostwald ripening and/or coalescence of Au NPs before nanowire nucleation, (ii) Au-catalysed VLS nucleation and axial growth of ZnO nanowires and (iii) radial growth of nanowires by a vapour–solid process. These processes originate the NP and nanowire size evolution during the experiments. The present findings are interpreted in terms of Zn vapour pressure changes during carbo-thermal evaporation. PACS 61.46.+w; 68.65.-k; 81.16.Dn     

高取向As掺杂ZnO纳米线阵列的制备与表征

在不采用任何金属催化剂的条件下,运用化学气相沉积法,在Si(100)衬底上制备出高取向的As掺杂ZnO纳米线阵列.样品的X射线衍射(XRD)谱显示获得了单一取向的衍射峰,表明样品具有较好的结晶质量.场发射扫描电镜(FE-SEM)观察表明,As掺杂ZnO纳米线阵列具有均一的直径和长度,其顶部和根部直径分别为70 nm和1...     

Strong blue emission from ZnSe nanowires grown at low temperature

We report optimized photoluminescence of ZnSe nanowires grown by molecular beam epitaxy, obtained by lowering the growth temperature down to 300 °C. The low‐temperature growth method has been developed using Si(111) and GaAs(111)B substrates. On the latter, vertical oriented blue‐emitting nanowires have been obtained. The growth mecha‐ nism is discussed with the help of in‐situ and ex‐situ electronic and structural measurements. We also report strong blue luminescence from ZnSe nanowires grown on ITO‐coated glasses, demonstrating that ZnSe nanowires are optimal candidates for transparent optoelectronics. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)