diff --git a/paper/method/default.typ b/paper/method/default.typ index 7d38d22..af48208 100644 --- a/paper/method/default.typ +++ b/paper/method/default.typ @@ -23,21 +23,24 @@ The Si/C ratios during growth were 0.7, 1.2, 1.6, 2.4, and 2.0 for the five wafe 大部分实验中,我们使用 532 nm 的激光,少部分实验中使用 325 nm 的激光以观测紫外拉曼。 有三个不同的入射配置,包括正入射、掠入射、边入射。 考虑到 4 度斜切和 4H-SiC 几乎各向同性的折射率(2.73) @shaffer_refractive_1971 ,掠入射的入射角大约为 25 度。 -在正散射过程中,我们使用 100 微米的共焦针孔,以尽可能提高 z 方向的分辨率 @song_depth_2020。 +在正散射过程中,我们使用 100 微米的共焦针孔,以尽可能提高 z 方向的分辨率 @song_depth_2020;其它情况使用常用的 200 微米针孔以提高信噪比。 +此外,在正入射和边入射时,拉曼散射信号较强,因此我们使用较短的积分时间(约 60 秒), + 而在掠入射时,拉曼信号较弱,因此使用较长的积分时间(约 300 秒)。 -All our Raman experiments were performed using a LabRAM HR Evolution system with back-scattering configuration, - where collected scattered light has a reversed wavevector direction compared to the incident light. -A 532 nm laser was used in most experiments, - while a 325 nm laser was used to observe Raman signals under ultraviolet excitation. -Three different incidece configurations were used, as shown in @figure-incidence, - including normal incidence, where the laser beam is perpendicular to the epitaxial surface; - grazing incidence, where the laser beam is nearly parallel to the epitaxial surface; - and edge incidence, where the laser beam is incident at the edge of the wafer, instead of the epitaxial surface. -Taking the 4° offcut angle - and the nearly isotropic refractive index 2.73 of 4H-SiC @shaffer_refractive_1971 into account, - the wavevector in 4H-SiC during grazing incidence is about 25° to the c axis. -During normal incidence, a 100 μm confocal pinhole was used to improve the z-direction resolution @song_depth_2020; - while during other configurations, 200 μm confocal pinhole was used to improve the signal-to-noise ratio. +All Raman experiments were conducted using a LabRAM HR Evolution system in a back-scattering configuration, + where the collected scattered light propagates in the opposite direction to the incident laser. +A 532 nm laser served as the primary excitation source, + while a 325 nm laser was employed for only ultraviolet Raman measurements. +Three distinct incidence configurations were utilized, as illustrated in @figure-incidence: + (i) normal incidence, where the laser incident perpendicularly to the epitaxial surface; + (ii) grazing incidence, where the laser incident nearly parallelly to the epitaxial surface; + and (iii) edge incidence, where the laser is incident at the wafer edge and perpendicularly to the edge surface. +Considering the 4° offcut angle and the nearly isotropic refractive index of 2.73 for 4H-SiC @shaffer_refractive_1971, + the refracted laser in 4H-SiC during grazing incidence forms an angle of approximately 25° with the c axis. +A 100 μm confocal pinhole was used for normal incidence to enhance axial (z-direction) resolution @song_depth_2020, + while a 200 μm pinhole was employed for the other configurations to improve the signal-to-noise ratio. +Besides, the integration time was set to 60 seconds for normal and edge incidence, + while it was extended to 300 seconds for grazing incidence due to the weaker Raman signal. #include "figure-incidence.typ"