// SiC 是很好的材料。
// 其中，4H-SiC 是SiC的一种多型，它的性质更好，近年来随着外延工艺的成熟而获得了更多的关注。
SiC is a promising wide-bandgap semiconductor material
  with high critical electric field strength and high thermal conductivity.
  It has been widely used in power electronic devices and has long attracted a lot of research
  @casady_status_1996 @okumura_present_2006.
The 4H-SiC has a wider bandgap, higher critical electric field strength,
  higher thermal conductivity, and higher electron mobility along the c-axis than other polytypes.
Currently, the 4H-SiC has gradually received more attention than other polytypes,
  thanks to the development of epitaxy technology and the increasing application in the new energy industry
  @tsuchida_recent_2018 @harada_suppression_2022 @sun_selection_2022. // TODO: 多引用一些近年来的文献，有很多

// 声子（量子化的原子振动）在理解晶体的原子结构以及热电性质方面起着重要作用。
// 声子可以通过多种实验技术来探测，包括 EELS、IR 吸收谱等。
// 拉曼光谱是最常用的方法，它提供了一种无损、非接触、快速和局部的声子测量方法，已被广泛用于确定晶体的原子结构（包括区分 SiC 的多型）。
Phonons (quantized atomic vibrations) play a fundamental role
  in understanding the atomic structure
    as well as the thermal and electrical properties
  of crystals (including 4H-SiC).
They could be probed by various experimental techniques,
  such as electron energy loss spectroscopy and infrared absorption spectroscopy.
Among these techniques,
  Raman spectroscopy is the most commonly used method,
  as it provides non-destructive, non-contact, rapid and spatially localized measurement of phonons
  that near the #sym.Gamma point in reciprocal space.
Studies in Raman scattering of 4H-SiC have been conducted since as early as 1983
  and have been widely employed to identification of different SiC polytypes.
// TODO: 增加引用文献

// 近年来，更多信息被从拉曼光谱中挖掘出来。
// LOPC 已经被用于快速估计 n 型 SiC 的掺杂浓度。
// 层错的拉曼光谱也已经被研究，可以被用于检测特定结构层错的存在和位置。
// 掺杂对拉曼光谱的潜在影响也已经被研究。
// 然而，拉曼光谱上仍有一些不知来源的峰；同时，一些也缺少一些理论上预测应该存在的峰。
// 此外，预测掺杂导致的新峰也没有说明原因。
Increasingly rich information has been extracted from Raman spectra of 4H-SiC.
Longitudinal optical phonon–plasmon coupling (LOPC) peek
  has been utilized to rapidly estimate the doping concentration in n-type SiC.
Peeks associated with some stacking faults have also been investigated
  and used to detect the presence and location of specific structural faults.
Moreover, the potential effects of doping on Raman spectra have been explored.
However, some unidentified peaks still appear in the Raman spectra,
  while certain phonon modes predicted by theory remain unobserved.
In addition, the origins of newly emerged peaks induced by doping are often unclear or unexplained.
// TODO: 多举例，增加引用文献

In this paper, we do some things. Especially we do something for the first time.
// TODO: 完善
