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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/82808


    Title: Structural Characterization of Transition Metal Nanoclusters Supported on Graphene/Ru(0001) and Al2O3/NiAl(100) by RHEED and STM
    Authors: RAHMAH, ALFIATUR;RAHMAH, ALFIATUR
    Contributors: 物理學系
    Keywords: 過渡金屬納米簇;石墨烯;Al2O3;RHEED;STM;Transition Metal Nanoclusters;Graphene;Al2O3;RHEED;STM
    Date: 2020-05-18
    Issue Date: 2020-06-05 17:15:16 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 負載型過渡金屬納米團簇由於其在一系列領域中的潛在應用而在近幾十年來得到了廣泛的研究。然而,這種負載的納米糰簇的詳細結構研究,特別是在催化模型系統中很稀少。在目前的工作中,我們在超高真空條件下利用反射高能電子衍射(RHEED),掃描穿隧顯微鏡(STM)研究了石墨烯/ Ru(0001)上的Rh和V納米糰簇以及Al2O3 / NiAl(100)基底上的Cu團簇的結構。團簇在300 K的蒸汽沉積到基板上時生長,結果表明,Rh團簇結構有序,在fcc相中生長,其(111)面與石墨烯表面平行;它們的晶格相對於整體Rh擴展了2.4%,晶格常數隨著退火和覆蓋率(尺寸)的增加而降低。相反地,V團簇在結構上是無序的,不產生特徵衍射圖。 V團簇的有序結構不會出現,因為V偏愛bcc相,而bcc結構的任何面在結構上都不能很好地匹配石墨烯的六邊形晶格。 Cu團簇也以fcc相生長,但它們的(001)和(111)面與氧化鋁表面平行,其中Cu(111)[01̅1] //θ- Al2O3(100)[01̅0]); Cu(111)[112̅] //θ-Al2O3(100)[01̅0];和Cu(001)[110] //θ- Al2O3(100)[010])。 Cu簇的晶格參數擴展到10.8%,平均高度從大約0.52nm開始直到0.97nm,而平均直徑從1.1nm開始到2.34nm。然後,團簇的密度在低覆蓋率下增加。當銅團簇退火至高溫時,其不在條狀突起上。;Supported transition metals nanoclusters have interested researcher in recent decades, because their potential applications in a range of fields. Nevertheless, detailed structural studies of such supported nanoclusters, particularly in model systems of catalysis, are few. In the present work, we investigate the structures of Rh and V nanoclusters on graphene/Ru(0001) and Cu ones on Al2O3/NiAl(100) substrates, with reflection high energy electron diffraction (RHEED), Scanning Tunneling Microscopy (STM) and under ultrahigh vacuum conditions. The clusters are grown on the deposition of vapors onto the substrates at 300 K. The results show that the Rh clusters are structurally ordered, growing in an fcc phase and having their (111) facets parallel to the graphene surface; their lattice expands, up to 2.4 %, relative to the bulk Rh and the lattice constant decreases with annealing and increased coverage (size). In contrast, the V clusters are structurally disordered, yielding no characteristic diffraction patterns. No ordered structure for V clusters arises because V prefers a bcc phase while no facets of a bcc structure match structurally well the hexagonal lattice of graphene. The Cu clusters also grow in an fcc phase but have (001) and (111) facets parallel to the alumina oxide, with Cu (111)[01 ̅1]// θ-Al2O3(100)[01 ̅0]); Cu(111)[112 ̅ ]//θ-Al2O3(100) [01 ̅0]; and Cu(001)[110]// θ-Al2O3 (100)[010]). The lattice parameters of Cu clusters expand up to 10.8%, with the average height start about 0.52 nm up to 0.97 nm whereas the average diameter starts from 1.1 nm to 2.34 nm and the clusters density the increases at low coverage. Then Cu clusters are not on the stripe protrusions when the clusters are annealed to high temperatures.
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