Path-Dependent Morphological Evolution of Se-Te Mesostructures Prepared by Inorganic Phototropic Growth

We describe herein a path-dependent "history" effect wherein the film morphology generated in the second step of a two-step inorganic phototropic growth process depends on a preexisting structure that has been first grown under different optical stimulation conditions. Se-Te generated with static illumination exhibited a highly anisotropic lamellar morphology with a characteristic feature pitch proportional to the input wavelength. Growth using first a short wavelength of light, followed by growth using a longer wavelength, resulted in the second-stage morphology exhibiting termination of lamellae formed during the first growth step. The lamellar pitch at the end of the second growth step was larger than that effected in the first step. In contrast, use of the same input wavelengths but in the opposite order produced no change in the feature pitch but rather only linear feature extension. Analysis of light absorption in simulated structures, in tandem with the empirical data, indicated that the history effect and asymmetric path dependence are a result of emergent nanophotonic processes at the growth interface that dynamically shape the optical field and direct morphological evolution of the photodeposit in a continuous feedback loop.