Electroreduction of Si(NCO)4 for Electrodeposition of Si

The electrochemical reduction and concomitant suitability of tetraisocyanatosilane, Si(NCO) 4 , as a precursor for Si electrodeposition has been examined. At T = 25 °C, voltammetric data indicated that the electroreductive pathway of Si(NCO) 4 paralleled the electroreduction of SiCl 4 , albeit with attenuated current densities. At T = 150 °C, the measured current density increased significantly due to coupled reaction likely involving an electropolymerization of the tetraisocyanato ligand. At either temperature, the electrochemical response of Si(NCO) 4 did not strongly depend upon the identity of the anion in the supporting electrolyte. A combination of chronoamperometric, electron microscopy, and X-ray photoelectron spectroscopy data were used to study the morphology and composition of the electrodeposited Si films at room temperature. The composition and morphology of the as-electrodeposited films were consistent with the formation of amorphous Si when using solid n + -Si electrodes, similar to what is observed during the electroreduction of SiCl 4 . Attempts to use Si(NCO) 4 for Si crystal growth by the electrochemical liquid-liquid-solid (ec-LLS) process with a liquid e -GaIn electrode resulted in no appreciable crystalline Si product. Although Si(NCO) 4 can be used for electrodeposition of amorphous Si onto solid electrodes at room temperature, more work is needed to identify conditions that would facilitate its use for ec-LLS.