This commit is contained in:
@@ -34,7 +34,7 @@ These phonons were categorized into two groups according to their electrical pol
|
||||
where atoms of the same species vibrated in phase,
|
||||
resulting in strong electrical polarization and observable effects in Raman spectra
|
||||
(colored lines in @figure-discont).
|
||||
The categorized was also illustrated and compared with Raman experiment in @fig-raman.
|
||||
The categorized was also illustrated and compared with Raman experiment in @figure-raman.
|
||||
|
||||
极性不同的模式有着不同的行为,因此被分开讨论。
|
||||
|
||||
|
||||
@@ -84,14 +84,14 @@ The calculated phonon frequencies were in good agreement with experimental value
|
||||
with a slight underestimation of 2-5%,
|
||||
which might be attributed to the known tendency of the PBE functional underestimating interatomic forces (cite).
|
||||
The calculated Raman tensors were also consistent with both experimental and theoretical results.
|
||||
Among negligible-polar modes, the E#sub[2]-3 mode exhibited the highest Raman intensity,
|
||||
Among negligible-polar modes, the E#sub[2]-3 mode showed the highest Raman intensity,
|
||||
followed by four modes with lower intensities that were also visible in normal incidence Raman experiments,
|
||||
including the E#sub[2]-1 mode, the E#sub[2]-2 mode, the E#sub[1]-1 mode, and the A#sub[1]-1 mode.
|
||||
The E#sub[1]-2 mode and E#sub[2]-4 mode were not visible in our Raman experiments,
|
||||
as they were located close to the most intense E#sub[2]-3 mode (only about 10 cm#super[-1] away)
|
||||
with very weak Raman intensities (only 0.1% and 0.6% of the E#sub[2]-3 mode, respectively).
|
||||
Additionally,
|
||||
the A#sub[1]-2 mode exhibited a very weak Raman intensity under the incident light with in-plane polarization
|
||||
the A#sub[1]-2 mode had only a very weak Raman intensity under the incident light with in-plane polarization
|
||||
(only 0.01),
|
||||
but showed an observable intensity when the polarization is along the z-axis (1.78).
|
||||
Thus, it was not typically observed in normal incidence Raman experiments (cite),
|
||||
@@ -100,16 +100,38 @@ Thus, it was not typically observed in normal incidence Raman experiments (cite)
|
||||
|
||||
不同方向的入射配置会导致微小但可观测的峰位差异。
|
||||
|
||||
非零长度的波矢(i.e. 参与散射的声子不在 Gamma 点)导致不同入射配置的峰位具有微小但可观测的差异,如色散图所示。
|
||||
相比于正入射,肩入射时,E2-1与E2-2的间距会减小、E2-2会展宽;E2-3会展宽,同时略微蓝移动。
|
||||
我们的计算结果为xxx,实验结果为xxx。
|
||||
微小但可观测的峰位移动应该存在于不同入射配置的峰位中,因为非零的波矢长度。
|
||||
在我们的计算中,相比于正入射,肩入射的E2-1与E2-2的间距会减小0.49,同时A1-1会红移0.19。
|
||||
在实验中,E2-1与E2-2的间距减少0.36,A1-1红移了xxxx。
|
||||
|
||||
// 186.38835388124227
|
||||
// 201.84270995851526
|
||||
Minor but observable peak shifts of negligible-polar phonons were expected between different incidence configurations,
|
||||
due to non-zero wavevector lengths.
|
||||
In our calculations, compared to normal incidence,
|
||||
the spacing between the E#sub[2]-1 mode and E#sub[2]-2 mode decreased by 0.49 cm#super[-1] under edge incidence,
|
||||
while the A#sub[1]-1 mode redshifted by 0.19 cm#super[-1].
|
||||
In our experiments, the spacing between the E#sub[2]-1 mode and E#sub[2]-2 mode decreased by 0.36 cm#super[-1],
|
||||
while the A#sub[1]-1 mode redshifted by xxxx cm#super[-1].
|
||||
|
||||
// 191.77252066290447
|
||||
// 199.03816532139587
|
||||
#include "figure-nopo-diff.typ"
|
||||
|
||||
E1为什么可以被看到。
|
||||
|
||||
E1在正入射中可以看到,尽管理论上不应该。
|
||||
这被认为是因为入射光并非完全沿z轴入射,由于衬底斜切和共聚焦汇聚角。
|
||||
通过向不同方向倾斜衬底,我们可以使这个峰变高或变低,如附图所示。
|
||||
此外,考虑到斜切方向(x方向),E1模式应该更容易在zxxz和zyxz中看到,而在zyyz中更难看到,这与实验一致。
|
||||
|
||||
The E#sub[1]-1 mode was observed in normal incidence Raman experiments, despite being theoretically forbidden.
|
||||
This was attributed to the fact that the incident light was not perfectly aligned along the z-axis,
|
||||
due to the substrate's slight tilt and the converging angle of the confocal setup.
|
||||
This was confirmed by tilting the substrate in different directions,
|
||||
which caused the peak to become more or less pronounced, as shown in the inset figure.
|
||||
Furthermore, considering the tilt direction (x-direction),
|
||||
the E#sub[1]-1 mode should be more easily observed in the zxxz and zyxz configurations,
|
||||
while being more difficult to detect in the zyyz configuration,
|
||||
which is consistent with our experimental observations.
|
||||
|
||||
#include "figure-e1.typ"
|
||||
|
||||
// 其它峰在其它章节中解释。
|
||||
//
|
||||
|
||||
@@ -11,6 +11,15 @@
|
||||
// 若考虑到到入射光不是严格沿着 z 方向,而是有一个小的角度(例如 10 度),则此时有一个声子模式沿着 x 方向,另外两个声子模式则为 y-z 两个方向的混合。
|
||||
// (没有在图上表示)
|
||||
|
||||
半导体中的强极性声子模式强烈地依赖于入射光的方向,
|
||||
这是由于半导体中原子之间的长程库伦相互作用所致,
|
||||
表现在散射光谱中,Gamma点附近不连续(见@figure-discont)。
|
||||
具体来说,当入射光沿着 z 方向时,起作用的是 A-Gamma 线上的声子模式(图中的上半部分的橘线),它们适用于群 C6v。
|
||||
这时会有一个 TO 模式(C6v 中的 E1)和一个 LO 模式(C6v 中的 A1)。
|
||||
而当沿着 y 方向入射时,起作用的是 Gamma-K 线上的声子模式(图中下半部分的橘线),它们不再适用于群 C6v,而只适用于群 C2v;
|
||||
这时将会出现三个模式,包括一个LO(沿y方向振动,对应C2v中的A1)和两个TO模式(根据振动方向,命名为B2-x和B2-y,对应C2v中的B1和B2)。
|
||||
当入射光不是严格沿着坐标轴方向,而是在xOy面内呈现一定的夹角时(掠入射,以及考虑了斜切的正入射),则此时有一个声子模式沿着 x 方向,另外两个声子模式则为 y-z 两个方向的混合。
|
||||
|
||||
Strong-polar phonon modes caused by different incident light directions are different,
|
||||
due to long-range Coulomb interactions between atoms in semiconductors,
|
||||
showing discontinuity in the scattering spectra near the #sym.Gamma point (see @figure-discont).
|
||||
@@ -28,15 +37,25 @@ For example, when the light is incident along the y direction (phonon modes on t
|
||||
When the light is incident along a direction between z and y,
|
||||
three phonon modes will exist, but vibration in the mixed direction.
|
||||
|
||||
理论上预测,不同入射时,会发生什么改变,峰之间的差距有多少;实验中观测到的,差距有多少。
|
||||
将理论/计算结果与实验对比。
|
||||
|
||||
// 实验发现的确是这样的。
|
||||
我们将计算与实验结果进行了对比。衬底中的LO峰与plasmon耦合形成LOPC峰,因此与计算结果大不相同。
|
||||
对于TO峰,在正入射中,它与E2-3模式的距离为xxx;在掠入射中,它与E2-3模式的距离为xxx。
|
||||
|
||||
Many Raman experiments on 4H-SiC with incident light along the z direction have observed two peaks.
|
||||
However, no experiments have reported three peaks with incident light along other directions.
|
||||
In our experiment, we found the third, and it satisfied properties we expected.
|
||||
In our experiments, we found that the third peak only appears when focusing inside the sample.
|
||||
|
||||
E1 的情况。
|
||||
|
||||
注意到在正入射中,理论上不能被观察到的E#sub[1]-1模式也被观察到了。
|
||||
与弱极性的 E1-1 模式类似,我们也认为这是由于入射光并非完全沿 z 轴入射所致。
|
||||
但与弱极性 E1-1 模式不同的是,强极性 E1-1 模式在 xy 的偏振下并没有更强反而更弱。
|
||||
这是因为E1这时不再是严格的E1模式,而是分裂成了两个相近的模式。
|
||||
我们的计算表明,在2度的入射角下,E1分裂的两个模式非常接近。
|
||||
其中某个模式会怎样怎样,另一个会怎样怎样。
|
||||
|
||||
// 我们预测,随着入射方向偏移,LO 峰会向着高频方向移动。此外,我们也注意到 LO 也会与载流子产生影响。
|
||||
// 在 n 型半导体中,LOPC 模式将代替 LO 模式;在 p 型半导体中,LO 模式仍然单独存在,但它的半高宽会受到载流子浓度的影响。
|
||||
|
||||
|
||||
@@ -15,7 +15,7 @@
|
||||
let lopc = [Yes#linebreak() (LOPC)];
|
||||
let overf = [Yes#linebreak() (overfocused)];
|
||||
table(columns: 19, align: center + horizon, inset: (x: 3pt, y: 5pt),
|
||||
m2[*Incident Direction*], m(4)[z], m(4)[y], m(9)[between z and y, 20#sym.degree to z],
|
||||
m2[*Incident Direction*], m(4)[z], m(5)[y], m(8)[between z and y, 20#sym.degree to z],
|
||||
m2[*Vibration Direction*],
|
||||
// TODO: check LO-TO mixed
|
||||
[TO (x)], [TO (y)], m2[LO (z)], m3[TO (z)], [TO (x)], [LO (y)], m3[TO (y-z mixed)], [TO (x)], m(4)[LO (y-z mixed)],
|
||||
|
||||
Reference in New Issue
Block a user