Direct Electrodeposition of Crystalline Groups IV and III-V Semiconductors by Electrochemical Liquid-Liquid-Solid Growth

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With the support from the Macromolecular, Supramolecular and Nanochemistry Program of the Division of Chemistry and the Solid State and Materials Research Program of the Division of Materials Research, Prof. Stephen Maldonado of the University of Michigan aims to develop a novel, low-energy method for the preparation of technologically important crystalline semiconducting materials. Semiconductors are important materials for the fabrication of batteries, solar cells, and ultrafast microelectronics. Currently, energy-intensive methods are required for preparing high quality covalent semiconductors. This project provides to graduate and undergraduate students research training in electrochemistry, materials science, and advanced electron microscopic methods relevant to the fields of energy conversion/storage and microelectronics. In addition to disseminating research results in the form of publications and presentations at national conferences, Prof. Maldonado aimes to develop a new laboratory exercise on making semiconductor devices to introduce electrochemistry in the undergraduate curriculum.This research explores the use of electrochemical liquid-liquid-solid (ec-LLS) deposition as a synthetic and low-energy crystal growth method of semiconductors. The appeal of ec-LLS method is that it is a one-pot approach in which liquid metals are used simultaneously as sources of electrons for the reduction of semiconductor feedstock and as media for growing semiconductor crystals even at low temperatures. There are three main thrusts in this project. The first thrust aims to identify strategies and ec-LLS deposition parameters that effect desirable properties in Group IV (Ge, Si) macroscale crystals and micro/nanowires. This knowledge is essential for the predictive control of the morphological, crystallographic, and electronic properties of crystalline covalent semiconductors prepared through ec-LLS method. The second thrust involves ex-situ and in-situ (e.g. within optical and transmission electron microscopes) analyses to follow the nucleation and crystal growth steps in ec-LLS directly and in real time. The correlation between the current-time data and the specific nucleation and crystal growth steps provides real time feedback on the effects of various physicochemical and electrochemical factors on the crystals formed from ec-LLS. The third thrust focuses on understanding and controlling ec-LLS processes for tailored III-V (GaAs, InAs, GaSb, InSb) nanoparticles and nanowires.