This commit is contained in:
@@ -55,5 +55,6 @@ todo
|
||||
关于正入射和侧入射的对比:拟合得到结果、画曲线图、画箱图
|
||||
极性模式对比。有两个方面需要对比。一个是,正、侧入射的不同,说明分裂的大小与我们的计算是否一致,LOPC是否会在其它偏振下出现;一个是,对正入射时E1的出现作解释。
|
||||
|
||||
散射光路对不同偏振的响应不同,因此需要乘以一个系数。
|
||||
|
||||
探索:为什么对于A1的拟合,结果会差两倍?
|
||||
@@ -1,47 +1,19 @@
|
||||
== Phonons in Perfect 4H-SiC
|
||||
|
||||
不同方向入射光的声子位置不同。我们只研究 Gamma 附近的那些。
|
||||
我们将声子被分为两类讨论:
|
||||
极性可以忽略的声子模式(即极性为零或非常弱的声子),在拉曼散射过程中它们的电极性造成的效应可以忽略;
|
||||
强极性声子模式,在拉曼光谱中电极性效应是可观测的,不可以被忽略。
|
||||
|
||||
参与拉曼散射的声子的波矢等于入射光与散射光的波矢差。
|
||||
因此,在我们的实验(绿光和紫外光的背散射)中,参与拉曼散射的声子都位于 Gamma 点附近,且不同的入射方向对应的声子波矢不同。
|
||||
对于正入射,声子大致位于 Gamma-A 线上;对于沿x方向的边入射,声子大致位于 Gamma-K 线上。对于掠入射,声子不位于任何高对称线上。
|
||||
|
||||
The wavevectors of phonons participating in Raman scattering
|
||||
equaled to the difference between the wavevectors of the incident and scattered light.
|
||||
Thus, in our experiments (back-scattering with green and UV light),
|
||||
the phonons involved were located very close to the #sym.Gamma point,
|
||||
with various wavevectors determined by the incidence configurations.
|
||||
As illustrated in @figure-discont, in Raman experiments of normal and edge incidence,
|
||||
the relevant phonons lied approximately at the #sym.Gamma–A and #sym.Gamma–K lines, respectively.
|
||||
For grazing incidence,
|
||||
the relevant phonons did not reside on any high-symmetry lines and were therefore not depicted in the figure.
|
||||
|
||||
#include "figure-discont.typ"
|
||||
|
||||
每个点都有 21 个声子模式。我们把它分成 18 个极性很小的和 3 个极性很强的两类。
|
||||
|
||||
对于每一个 Gamma 附近的点,都有 21 个声子模式(简并模式按简并数计)。
|
||||
我们将这 21 个声子模式分为两类:18 个极性可以忽略的声子模式(即极性为零或非常弱的声子),在拉曼散射过程中它们的电极性造成的效应可以忽略;
|
||||
和 3 个强极性声子模式,在拉曼光谱中电极性效应是可观测的。
|
||||
|
||||
At each position near the #sym.Gamma point, there were 21 phonon modes with non-zero frequency (counting degeneracies).
|
||||
These phonons were categorized into two groups according to their electrical polarities:
|
||||
18 negligible-polar phonons (i.e., zero or very weak electrical polarity),
|
||||
These phonons were categorized into two groups and discussed separately, according to their electrical polarities:
|
||||
phonons with negligible polarities (i.e., zero or very weak electrical polarity),
|
||||
where atoms of the same species vibrated in opposite directions,
|
||||
resulting in effective cancellation of electrical polarization during the Raman process
|
||||
(gray lines in @figure-discont);
|
||||
and three strong-polar phonons,
|
||||
and phonons with strong polarities
|
||||
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 @figure-raman.
|
||||
|
||||
极性不同的模式有着不同的行为,因此被分开讨论。
|
||||
|
||||
Negligible-polar and strong-polar phonons exhibited distinct behaviors
|
||||
and were therefore discussed separately in the following sections.
|
||||
|
||||
#include "figure-raman.typ"
|
||||
|
||||
#include "figure-discont.typ"
|
||||
#include "non-polar/default.typ"
|
||||
#include "polar/default.typ"
|
||||
|
||||
@@ -4,8 +4,10 @@
|
||||
(a) Phonon dispersion of 4H-SiC along the A–#sym.Gamma–K high-symmetry path.
|
||||
(b) Magnified view of the boxed region in (a).
|
||||
(c) Magnified view of the boxed region in (b).
|
||||
The orange dashed lines mark the phonon wavevectors involved in Raman scattering
|
||||
with green laser light under normal and edge incidence configurations.
|
||||
The orange dashed lines marked the phonon wavevectors involved in Raman scattering
|
||||
with green laser light (532 nm) under normal and edge incidence configurations.
|
||||
The phonons relevant to grazing incidence configuration did not reside on any high-symmetry lines
|
||||
and were therefore not depicted in the figure.
|
||||
],
|
||||
placement: none,
|
||||
)<figure-discont>
|
||||
|
||||
@@ -1,5 +1,7 @@
|
||||
=== Phonons with Negligible Polarities
|
||||
|
||||
对弱极性声子的分析首先从理论出发,然后结合
|
||||
|
||||
对弱极性声子的理论分析,首先使用 Gamma 点的声子来近似,然后再讨论不同入射方向导致的差异。
|
||||
使用Gamma 点的声子来近似,基于这样的事实:这些声子的色散曲线在 Gamma 点附近连续且非常接近 Gamma 点,并且已经被广泛使用 @_n-sic_2008。
|
||||
|
||||
@@ -8,7 +10,7 @@ Negligible-polar phonons were theoretically analyzed,
|
||||
followed by a discussion of modifications arising from non-zero wavevectors.
|
||||
This approximation is based on the fact that
|
||||
the dispersion of these phonons is continuous and very close to the #sym.Gamma point,
|
||||
and has been widely adopted in the literature @_n-sic_2008.
|
||||
and has been widely adopted in the literature @_n-sic_2008.
|
||||
|
||||
18 个声子属于 12 个表示。拉曼张量的形状可以确定,大小不能。
|
||||
|
||||
@@ -43,7 +45,7 @@ It should be noted, however, that the observability in Raman experiment depends
|
||||
每个原子对拉曼张量的贡献主要取决于第一近邻原子(它们的贡献记为 $a_i$),更远的原子则归结为小量(记为 $epsilon_i$ $eta_i$ $zeta_i$)。
|
||||
此外,我们忽略了同一个振动模式中,同种原子振幅的绝对值的差异,只考虑它们振动方向的不同。
|
||||
因此,拉曼张量的大小可以在进一步的第一性原理计算之前给出,结果总结在表中。
|
||||
我们的结果表明,E2-3 模式的拉曼散射强度远高于其它振动模式,这与实验一致。
|
||||
我们的结果表明,E2-3 模式的拉曼散射强度远高于其它振动模式,这与实验和第一性原理计算结果一致。
|
||||
我们的研究表明,这个峰的高拉曼强度来自于所有键的贡献的相长干涉,这与其他弱极性模式不同(他们的贡献相互抵消)。
|
||||
|
||||
A method to estimate the magnitudes of the Raman tensors of each mode from their vibration patterns (eigenvectors)
|
||||
@@ -55,26 +57,54 @@ Furthermore, the absolute amplitude differences among atoms of the same type wit
|
||||
and only their vibrational directions were considered.
|
||||
This enables a preliminary estimation of the Raman tensor magnitudes prior to detailed first-principles calculations,
|
||||
with the results summarized in @table-nopol.
|
||||
Our analysis gave the result that the E#sub[2]-3 mode (at about 756.25 cm#super[-1] in simulation)
|
||||
Our analysis gave the result that the E#sub[2]-3 mode
|
||||
should possess a much higher Raman scattering intensity than the others,
|
||||
which is consistent with experimental observations,
|
||||
where at about 776 cm#super[-1] a very strong E#sub[2] peak is observed.
|
||||
which is consistent with experimental and first-principles calculation results in the following text.
|
||||
Our result showed that
|
||||
the high Raman intensity of this mode arises from the constructive interference of contributions from all bonds,
|
||||
in contrast to other negligible-polar modes where contributions tend to cancel each other out.
|
||||
|
||||
#include "table-nopol.typ"
|
||||
|
||||
我们使用第一性原理计算得到了频率和拉曼张量的大小,并与我们的结果进行了比较。
|
||||
我们做了计算,估计哪些峰可以看到、哪些峰看不到。
|
||||
|
||||
声子频率和拉曼张量的大小被使用第一性原理计算,并与实验结果和理论预测进行了比较(@table-nopol)。
|
||||
使用第一性原理计算得到了声子频率和拉曼张量的大小。
|
||||
我们的计算表明,E#sub[2]-1 E#sub[2]-2 E#sub[1]-1 A#sub[1]-1 E#sub[2]-3 模式的拉曼强度较高,并且被报道在绝大多数的拉曼实验中可以看到。
|
||||
A#sub[1]-2 被报道在一些实验中可以观测到而在另外一些实验中不可以观测到(cite)。
|
||||
我们的计算表明它在面内偏振下拉曼散射强度非常弱,但在 z 轴偏振下有可观测的强度;
|
||||
因此在正入射拉曼实验中可能难以看到,但在侧入射时通过选取合适的偏振配置应该可以观察到。
|
||||
E#sub[1]-2 和 E#sub[2]-4 模式位于最强模式 E#sub[2]-3 附近,且具有很弱的拉曼强度(分别为最强模式的0.1%和0.6%),在报道的实验中都不可见。
|
||||
E#sub[1]-2 与最强模式 E#sub[2]-3 表示不同,我们认为,通过选取合适的偏振配置,可能可以在实验中观察到。
|
||||
|
||||
The Raman tensors and frequencies of the negligible-polar phonons were calculated using first-principles methods.
|
||||
The results showed that
|
||||
the E#sub[2]-1, E#sub[2]-2, E#sub[1]-1, A#sub[1]-1, and E#sub[2]-3 modes possess relatively high Raman intensities
|
||||
The calculated phonon frequencies were in good agreement with experimental values,
|
||||
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 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 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),
|
||||
but could be clearly detected in edge incidence configurations in our experiments.
|
||||
|
||||
|
||||
我们做了实验,比别人多看到了几个峰;和计算结果比对良好。
|
||||
|
||||
拉曼散射实验在衬底上进行,并与第一性原理计算结果进行了比较。
|
||||
在我们的实验中,除了 E#sub[2]-4 以外的弱极性模式对应的拉曼散射峰都被观察到,多于其它实验;
|
||||
这包括 A#sub[1]-2 在 xzzx 下可以观察到,
|
||||
以及 E#sub[1]-2 在 xzyx 下通过额外延长积分时间而观察到。
|
||||
计算的声子频率与实验数据有很好的吻合,误差在 2-5% 之间,这个误差可能是由于 PBE 泛函对原子间力的低估(cite)。
|
||||
计算的拉曼张量也与实验和理论结果基本一致,这包括强度最高的模式 E#sub[2]-3,
|
||||
其次是四个强度较低但在实验中清晰可见的模式,包括 E#sub[2]-1、E#sub[2]-2、E#sub[1]-1 和 A#sub[1]-1。
|
||||
E#sub[1]-2 和 E#sub[2]-4 模式位于最强模式 E#sub[2]-3 附近,且具有很弱的拉曼强度(分别为最强模式的0.1%和0.6%),
|
||||
使得它们在实验光谱中难以区分。
|
||||
此外,A#sub[1]-2 模式在基面极化配置(xx 和 yy,仅为 0.01)中具有非常弱的拉曼强度,这导致它在正入射的拉曼实验中通常不可见;
|
||||
但当偏振沿 z 轴时(1.78)则显示出可观测的强度。
|
||||
计算的拉曼张量也与实验和理论结果基本一致。
|
||||
|
||||
The Raman tensors and frequencies of the negligible-polar phonons were calculated using first-principles methods,
|
||||
and the results were compared with both experimental data and theoretical predictions (@table-nopol).
|
||||
@@ -95,15 +125,20 @@ Additionally,
|
||||
Thus, it was not typically observed in normal incidence Raman experiments (cite),
|
||||
but could be clearly detected in edge incidence configurations in our experiments.
|
||||
|
||||
理想情况下不允许存在的效应被观察到。
|
||||
这包括不同入射方向下,弱极性峰位的微小移动,以及 E#sub[1]-1 模式在正入射中的可见性。
|
||||
#include "figure-raman.typ"
|
||||
|
||||
E#sub[1]-1 模式在正入射中可见。
|
||||
|
||||
E#sub[1]-1 模式在正入射拉曼实验中被观察到尽管在理论上是不允许的,这被认为是因为入射光并非完全沿c轴入射。
|
||||
如图所示,由于非零的数值孔径,激光汇聚到样品上时存在一个锥形角度(不完全平行于c轴),使得 E#sub[1]-1 模式在正入射中总是可见的。
|
||||
由于衬底斜切(沿着x方向),对于 zxxz 和 zxyz 配置,入射光或散射光的偏振将具有更多的 z 分量,从而使 E#sub[1]-1 模式的强度增加。
|
||||
通过略微倾斜衬底可以补偿斜切导致的效应,如附图所示。
|
||||
|
||||
不同入射方向下弱极性峰位的微小移动被观察到,这是由于非零波矢长度的声子引起的。
|
||||
在我们的计算中,从正入射到肩入射,E2-3的峰位几乎不变,E2-1与A1-1会有可观测的蓝移,同时E2-2会有可观测的红移。
|
||||
实验结果与计算结果基本一致,如图如表所示。
|
||||
E1模式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。
|
||||
不同方向偏振的结果印证了我们的猜想,如图所示。同时,略微倾斜衬底可以使这个峰变高或变低,如附图所示,这印证了我们的猜想。
|
||||
|
||||
Some effects absent in the ideal model were observed experimentally,
|
||||
Some effects absent in previous theory were observed experimentally,
|
||||
including minor but observable peak shifts of negligible-polar phonons between different incidence configurations,
|
||||
and the observability of the E#sub[1]-1 mode in normal incidence Raman experiments.
|
||||
The peak shifts were considered caused by the non-zero wavevector lengths of phonons.
|
||||
|
||||
@@ -39,7 +39,7 @@
|
||||
[0.17], [1.13], [2.43], [2.83], [1.79], [0.09], [88.54], [0.50], [0.01], [1.78],
|
||||
[Experiment result #linebreak() (a.u.)],
|
||||
// E2 E2 E1 A1 E1 E2 E2 A1
|
||||
[0.15], [1.11], [0.68], [1.64], [3.15], [Invisible], [88.54], [Invisible], [Invisible], [2.97],
|
||||
[0.15], [1.11], [0.68], [1.64], [3.15], [ ], [88.54], [Invisible], [Invisible], [2.97],
|
||||
table.cell(rowspan: 2)[*Raman Shift of Different Incidence Directions*],
|
||||
[Calculation result (cm#super[-1])],
|
||||
// E2 E2 E1 A1 E1 E2 E2 A1
|
||||
|
||||
BIN
画图/声子不连续/embed.svg
LFS
BIN
画图/声子不连续/embed.svg
LFS
Binary file not shown.
BIN
画图/声子不连续/main.svg
LFS
BIN
画图/声子不连续/main.svg
LFS
Binary file not shown.
BIN
画图/弱极性不同方向偏移/plot.ipynb
LFS
BIN
画图/弱极性不同方向偏移/plot.ipynb
LFS
Binary file not shown.
BIN
画图/弱极性不同方向偏移/拉曼.svg
LFS
BIN
画图/弱极性不同方向偏移/拉曼.svg
LFS
Binary file not shown.
BIN
画图/拉曼整体图/latex文字.svg
LFS
Normal file
BIN
画图/拉曼整体图/latex文字.svg
LFS
Normal file
Binary file not shown.
BIN
画图/拉曼整体图/main.svg
LFS
BIN
画图/拉曼整体图/main.svg
LFS
Binary file not shown.
BIN
画图/拉曼整体图/plot.ipynb
LFS
BIN
画图/拉曼整体图/plot.ipynb
LFS
Binary file not shown.
BIN
画图/拉曼整体图/拉曼-报告.svg
LFS
BIN
画图/拉曼整体图/拉曼-报告.svg
LFS
Binary file not shown.
BIN
画图/拉曼整体图/拉曼.svg
LFS
BIN
画图/拉曼整体图/拉曼.svg
LFS
Binary file not shown.
BIN
画图/拉曼整体图/拉曼E12.svg
LFS
Normal file
BIN
画图/拉曼整体图/拉曼E12.svg
LFS
Normal file
Binary file not shown.
BIN
画图/拉曼整体图/拉曼小A1.svg
LFS
BIN
画图/拉曼整体图/拉曼小A1.svg
LFS
Binary file not shown.
10
画图/拉曼结果拟合/251008/3/zxxz_x.txt
Normal file
10
画图/拉曼结果拟合/251008/3/zxxz_x.txt
Normal file
File diff suppressed because one or more lines are too long
10
画图/拉曼结果拟合/251008/3/zxxz_y.txt
Normal file
10
画图/拉曼结果拟合/251008/3/zxxz_y.txt
Normal file
File diff suppressed because one or more lines are too long
10
画图/拉曼结果拟合/251008/3/zxyz_x.txt
Normal file
10
画图/拉曼结果拟合/251008/3/zxyz_x.txt
Normal file
File diff suppressed because one or more lines are too long
10
画图/拉曼结果拟合/251008/3/zxyz_y.txt
Normal file
10
画图/拉曼结果拟合/251008/3/zxyz_y.txt
Normal file
File diff suppressed because one or more lines are too long
Binary file not shown.
@@ -52,7 +52,13 @@
|
||||
* 1: 摆拍几张照片
|
||||
* 2: 衬底侧入射 xzzx xzyx 离焦 0 针孔 100 积分时间 5 积分次数 10 范围 150-650 580-1050 11 个点
|
||||
* 3: 衬底正入射 zxxz zxyz 离焦 0 针孔 100 积分时间 5 积分次数 10 范围 150-650 580-1050 11 个点
|
||||
* 251019:
|
||||
* 1: 衬底侧入射 xzyx 观察 E12 离焦 0 针孔 100 积分时间 30 积分次数 10 范围 600-790 5 个点
|
||||
* 2: 正入射衬底,将zxxz稍微垫高一点的结果。垫高x方向的某个方向。先分别测试不垫高和垫高的结果,确认有明显差别后再多测试几个点。
|
||||
* 3: 衬底正入射,离焦 0 针孔 100 积分时间 5 积分次数 10 范围 580-1050,1 是衬底,其余依次是 532 631 230 126 206 取 11 个点。
|
||||
* 4: 外延层侧入射,
|
||||
* 2510xx:
|
||||
* 1: 正入射衬底,将zxxz稍微垫高一点的结果。垫高x方向的某个方向。
|
||||
* 2: 外延层侧入射。
|
||||
* 3: 衬底侧入射 xzyx 延长积分时间以得到 E12
|
||||
|
||||
|
||||
Reference in New Issue
Block a user