Guzman Erick, Kargar Fariborz, Angeles Frank, Meidanshahi Reza Vatan, Grotjohn Timothy, Hardy Aaron, Muehle Matthias, Wilson Richard B, Goodnick Stephen M, Balandin Alexander A
Nano-Device Laboratory and Phonon Optimized Engineered Materials Center, Department of Electrical and Computer Engineering, University of California, Riverside, California 92521, United States.
Department of Mechanical Engineering and Materials Science and Engineering Program, University of California, Riverside, California 92521, United States.
ACS Appl Mater Interfaces. 2022 Sep 21;14(37):42223-42231. doi: 10.1021/acsami.2c10879. Epub 2022 Sep 9.
We report the results of the investigation of bulk and surface acoustic phonons in the undoped and boron-doped single-crystal diamond films using the Brillouin-Mandelstam light scattering spectroscopy. The evolution of the optical phonons in the same set of samples was monitored with Raman spectroscopy. It was found that the frequency and the group velocity of acoustic phonons decrease nonmonotonically with the increasing boron doping concentration, revealing pronounced phonon softening. The change in the velocity of the shear-horizontal and the high-frequency pseudo-longitudinal acoustic phonons in the degenerately doped diamond, as compared to that in the undoped diamond, was as large as ∼15% and ∼12%, respectively. As a result of boron doping, the velocity of the bulk longitudinal and transverse acoustic phonons decreased correspondingly. The frequency of the optical phonons was unaffected at low boron concentration but experienced a strong decrease at the high doping level. The density-functional-theory calculations of the phonon band structure for the pristine and highly doped samples confirm the phonon softening as a result of boron doping in diamond. The obtained results have important implications for thermal transport in heavily doped diamond, which is a promising material for ultra-wide-band-gap electronics.
我们报告了使用布里渊 - 曼德尔斯坦光散射光谱对未掺杂和硼掺杂的单晶金刚石薄膜中的体声子和表面声子进行研究的结果。用拉曼光谱监测了同一组样品中光学声子的演化。发现声子的频率和群速度随着硼掺杂浓度的增加而非单调地降低，这表明存在明显的声子软化现象。与未掺杂的金刚石相比，简并掺杂金刚石中水平剪切声子和高频准纵向声子的速度变化分别高达约15%和约12%。由于硼掺杂，体纵向和横向声子的速度相应降低。在低硼浓度下，光学声子的频率不受影响，但在高掺杂水平下会大幅降低。对原始样品和高掺杂样品的声子能带结构进行的密度泛函理论计算证实了金刚石中硼掺杂导致的声子软化。所获得的结果对重掺杂金刚石中的热传输具有重要意义，重掺杂金刚石是超宽带隙电子学中有前景的材料。
