The work function of hydrothermally synthesized UO₂ and the implications for semiconductor device fabrication

Abstract

The photoelectric work function of nearly stoichiometric (111) and (100) hydrothermally grown UO2 was measured to be 6.28 ± 0.36 eV and 5.80 ± 0.36 eV, respectively. Candidate metals for electrical contacts are identified for both rectifying and non‐rectifying contacts based on work function, lattice compatibility, and electrical conductivity.

二氧化铀-钯-石墨烯纳米复合材料的合成及其催化4-硝基苯酚还原反应的研究

“…Conventionally, Pd is regarded as the catalytic site to react with BH 4 by accepting electrons which transfer to 4-nitrophenol subsequently. In our catalysts, an electron transfer from palladium to uranium may take place since that Pd (5.12 eV) has a lower work function than UO2 (6.68 eV) [40,41]. It is known that Fermi level alignment occurs whenever a metal and a semiconductor are placed in contact, resulting in charge redistribution and formation of a depletion layer surrounding the metal [42].…”

Interband Transitions And Critical Points Of Single Crystal Thoria Compared To Urania

“…Absorption of UO2 thin films, by optical transmission has also been measured [14], while the optical properties for both ThO2 and UO2 have been previously calculated [15] using the Heyd-Scuseria-Ernzerhof (HSE) functional. The challenges of growing uranium oxide singlecrystals have been addressed with the fabrication of high-quality, single crystal actinide oxide samples using a hydrothermal synthesis growth technique [12,13,[16][17][18][19][20][21][22]. This growth process has produced bulk single crystals of near-stoichiometric UO2 [12,13,17,[20][21][22] and ThO2 [13,18,19,22].…”

“…The challenges of growing uranium oxide singlecrystals have been addressed with the fabrication of high-quality, single crystal actinide oxide samples using a hydrothermal synthesis growth technique [12,13,[16][17][18][19][20][21][22]. This growth process has produced bulk single crystals of near-stoichiometric UO2 [12,13,17,[20][21][22] and ThO2 [13,18,19,22]. These improved single crystals make higher quality assessments of the UO2 and ThO2 optical and semiconductor properties possible, as defect contributions to the complex dielectric function are much suppressed [13].…”

Research Progress of Hyperstoichiometric UO2Crystals

“…pected to enhance the understanding of the material and provide the possibility of great potential applications in solar cells, thermoelectric devices and future electronics. [4] 。 2014 年 11 月, 美国科学家在 Science 上连续发表 UO 2 高温特性、结构等研究成果 [5][6] 。此 外, 核废料处理也是核电发展的一个重要课题。核 电站每年产生大量的贫铀(Depleted UO 2 , DUO 2 )需 要处理, 传统密封深埋措施存在很多隐患。变废为 宝、开发氧化铀的应用是核废料处理的发展趋势。 事实上, 除了作为核燃料, UO 2 还是性能优异的半 导体材料和热电材料 [7][8] [7,[9][10][11] , 但是晶体尺 寸都比较小, 质量也不高。Young 等 [11] 利用水热法 生长(111)和(100)晶面的 UO 2 单晶(UO 2.003 ), 测得其 光电功函数分别为(6.28±0.36) eV 和(5.80±0.36) eV, 为 UO 2 单晶的半导体器件应用提供参考。 Robins 等 [12] 通过在熔融碱金属氯化物熔体中电解氯化铀酰获得 3 mm 长的单晶。Kavazauri 等 [13] 研究了不同化学计 量比 UO 2+x 样品, 发现热扩散率和热导率随着 x 增 加而降低。Kruschwitz 等 [14] [15][16][17] 。在 UO 2 和 UO 3 之间, 有大量的相结构, 主要包括萤石相 (O/U=2~2.5)和层状结构(O/U=2.5~3)两种 [18][19] 。其中, 图 1 U-O 体系的相图 [15][16][17] Fig. 1 The phase diagram of U-O [15][16][17] UO 2 是面心立方萤石结构, 空间群为 Fm-3m, 晶格 参数 a=b=c=0.547 nm, 在室温条件下可以稳定存在, 熔点为 2878 ℃ [20] 。 U 4 O 9 有 α、 β 和 γ 三种相结构 [21] ; U 3 O 8 主要是 α 和 β 两种相结构 [22] ; UO 3 则有 7 种晶 型结构和 1 个非晶相 [19] [30] 。Teixeira 等 [31] [34] 。α-U 3 O 8 能在 400 ℃稳 定 存 在 [35]…”