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Synthesis and characterization of hexagonal boron nitride for integration with graphene electronics.

机译：与石墨烯电子器件集成的六方氮化硼的合成与表征。

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摘要

Hexagonal boron nitride (h-BN) has attracted increased interest as a dielectric material to graphene electronics. Traditional dielectrics, such as SiO2 or various high-k materials, can introduce scattering from charged surface states, impurities, surface optical phonons, and substrate roughness; significantly degrading the transport properties of graphene. Hexagonal boron nitride boasts several key advantages over SiO2 and high-k dielectrics. Most notably, it exhibits an atomically smooth surface that is expected to be free of dangling bonds, leading to an interface that is relatively free of surface charge traps and adsorbed impurities. Additionally, h- BN's high energy surface optical phonon modes lead to reduced phonon scattering from the dielectric. Using h-BN (grown via CVD on copper foil) as a gate dielectric to quasi-freestanding epitaxial graphene (QFEG) devices, a >2.5x increase in intrinsic current gain cut-off frequency and a >3x increase in mobility over HfO2 gated devices is obtained.;In addition, this thesis presents the transfer-free deposition of boron nitride on sapphire and silicon for use as a supporting substrate to CVD-grown graphene. This is accomplished via a polymer-to-ceramic conversion process involving the deposition of polyborazylene at low temperature (≤400°C) and subsequent annealing at 1000°C to BN. Atomic force microscopy (AFM) confirms the deposition of an ultra smooth (RMS roughness <130pm) h-BN film without the need for a solution-based transfer process. However, x-ray photoelectron spectroscopy (XPS) shows that the stoichiometry is dependent on the initial polyborazylene deposition temperature. Despite a turbostratic structure and a boron-rich stoichiometry, CVD graphene transferred to boron nitride films deposited on Al2O3 at a polyborazylene deposition temperature of 400°C is nearly strain-free and results in an improvement in mobility of >1.5x and >2.5x compared to CVD graphene transferred to bare Al2O3 and SiO2, respectively, due to a low impurity density and reduced surface optical phonon scattering.
机译：六方氮化硼（h-BN）作为石墨烯电子器件的介电材料吸引了越来越多的关注。传统的电介质，例如SiO2或各种高k材料，会从带电的表面态，杂质，表面光子和表面粗糙度引入散射。显着降低了石墨烯的传输性能。六方氮化硼比SiO2和高k电介质具有几个关键优势。最值得注意的是，它显示出原子上光滑的表面，预期该表面没有悬空键，从而导致界面上相对没有表面电荷陷阱和吸附的杂质。另外，h-BN的高能表面光子声子模导致声子从电介质的散射减少。使用h-BN（通过CVD在铜箔上生长）作为准独立式外延石墨烯（QFEG）器件的栅极电介质，本征电流增益截止频率增加> 2.5倍，并且在HfO2栅极上的迁移率增加> 3倍此外，本文提出了氮化硼在蓝宝石和硅上的无转移沉积，用作CVD生长的石墨烯的支撑衬底。这是通过聚合物到陶瓷的转化过程完成的，该过程包括在低温（≤400°C）下沉积聚硼氮烯并随后在1000°C退火至BN。原子力显微镜（AFM）证实可以沉积超光滑（RMS粗糙度<130pm）h-BN膜，而无需基于溶液的转移过程。但是，X射线光电子能谱（XPS）显示，化学计量取决于初始聚硼氮烯的沉积温度。尽管具有涡轮层结构和富硼化学计量关系，但在400℃的聚硼氮烯沉积温度下转移到沉积在Al2O3上的氮化硼膜上的CVD石墨烯几乎没有应变，并且迁移率提高了> 1.5x和> 2.5x与CVD石墨烯相比，由于低杂质密度和减少的表面光学声子散射，它们分别转移到裸露的Al2O3和SiO2中。

著录项

  • 作者

    Bresnehan, Michael S.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Engineering Materials Science.;Engineering General.;Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 244 p.
  • 总页数 244
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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