Biquard Xavier, Tuaz Aymeric, Ballet Philippe
Université Grenoble Alpes, CEA, IRIG, MEM, NRS, 38000 Grenoble, France.
Université Grenoble Alpes, CEA, LETI, 38000 Grenoble, France.
J Appl Crystallogr. 2022 Oct 1;55(Pt 5):1297-1304. doi: 10.1107/S1600576722008184.
Micro-Laue diffraction has been used to record cross-section profiles on a quasi-lattice-matched HgCdTe/CdZnTe heterostructure as a function of the stress induced by a flexion machine. The heterostructure may be decomposed into four different regions according to depth. Sufficiently far from the interface, the CdZnTe substrate is undisturbed by the HgCdTe layer, while the region situated 10 µm beneath the interface presents an in-plane lattice parameter adjustment to the +0.02% mismatched layer. The layer has a 2 µm critical thickness and, beyond, misfit dislocations induce a large peak broadening whose main direction changes with depth. The same occurs over the whole heterostructure once flexion-induced plastification has started. Consequently, the usual full width at half-maximum or integral breadth is no longer relevant, and only a newly defined and rotationally invariant 2D integral breadth correctly measures the plastification-induced peak broadening. Taking into account only the critical thickness region, a 15.1 ± 0.7 MPa tensile HgCdTe elastic limit was measured, slightly overestimated because of the initial compressive layer stress. It was observed that the plastic onset of the substrate perfectly matches the elastic limit of the layer, despite the fact that the substrate elastic limit is expected to be four times higher: a striking demonstration of the propagation of threading dislocations. The 'plastification easiness' is found to be 2.4 times smaller deep inside the substrate than in the layer critical thickness region, while in the substrate lattice adjustment region, the plastification easiness goes from the substrate to the layer value with a 22-25 MPa transition interval. This novel method using the 2D integral breadth allows for easy critical thickness measurement as well as precise plastic onset determination and plastification easiness assessment. It is a quite general method, since it may be applied to the vast class of epitaxial layers for which the critical thickness is larger than the micro-Laue beam size (currently 250 nm).
微劳厄衍射已被用于记录准晶格匹配的碲镉汞/碲锌镉异质结构上的横截面轮廓，该轮廓是弯曲机所施加应力的函数。根据深度，该异质结构可分解为四个不同区域。在离界面足够远的地方，碲锌镉衬底不受碲镉汞层的干扰，而在界面下方10 µm处的区域，其面内晶格参数向失配度为+0.02%的层进行了调整。该层具有2 µm的临界厚度，超过此厚度，失配位错会导致峰显著展宽，其主要方向随深度变化。一旦弯曲诱导的塑化开始，整个异质结构都会出现这种情况。因此，通常的半高宽或积分宽度不再适用，只有新定义的、旋转不变的二维积分宽度才能正确测量塑化诱导的峰展宽。仅考虑临界厚度区域，测得碲镉汞的拉伸弹性极限为15.1 ± 0.7 MPa，由于初始压缩层应力，该值略有高估。据观察，衬底的塑性起始与层的弹性极限完美匹配，尽管预计衬底的弹性极限要高四倍：这是穿通位错传播的一个显著例证。发现衬底内部深处的“塑化难易程度”比层临界厚度区域小2.4倍，而在衬底晶格调整区域，塑化难易程度从衬底值过渡到层值，过渡区间为22 - 25 MPa。这种使用二维积分宽度的新方法便于进行临界厚度测量以及精确确定塑性起始和评估塑化难易程度。这是一种相当通用的方法，因为它可应用于临界厚度大于微劳厄光束尺寸（目前为250 nm）的大量外延层。
