Bragg-Brentano (BB) geometry,反射式,通常的粉末和固体样品采用这种方法,光源和探测器在样品同侧,一种是样品平放,光管和探测器与样品夹角theta同时动,一种是光源不同,样品转theta角,探测器以两倍速度同时转,原理一样,探测器接收到的都是与光源偏离2theta角度处的衍射强度,
The penetration depth of x-rays is often found in the 10 .. 100 µm range. In most thin film investigations the thickness is substantially lower causing a large fraction of the diffractogram as measured in the symmetric θ/2θ configuration to stem from the substrate. Especially for the analysis of thin films x-ray diffraction techniques have been developed for which the primary beam enters the sample under very small angles of incidence. In its simplest variant this configuration is denoted by GIXRD that stands for grazing incidence x-ray diffraction. The small entrance angle causes the path traveled by the x-rays to significantly increase and the structural information contained in the diffractogram to stem primarily from the thin film.
入射的角度,视样品的厚度和材料线吸收系数,控制不同的入射角度可以探测不同的样品深度的信息,探测器旋转测量2theta角衍射信息,
采用反射式x光打入样品比较深,举例来说,铜靶x光源钢铁穿透深度是10um,薄膜的信号探测不到,掠入射的优点也在于克服了这个挑战,x光贴着样品打进去,入射角越小,x能探测到的越接近表面信号
xrdgixrd