Molybdenum diselenide formation using electrochemical atomic layer deposition (E-ALD)

•CV of Au in Mo and Se precursor solutions were examined at different pH.•E-ALD cycle chemistry was developed to electrodeposit MoSe2 thin films.•Presence of MoSe2 in as-deposited films was confirmed by PEC measurements.•Thermal annealing led to an enrichment of MoSe2 in the deposits.•Se can be used to induce Mo deposition, concomitantly forming MoSe2.

Cyclic voltammetry (CV) of Au in MoO3 and SeO2 solutions was studied under both basic and acidic conditions, as a precursor to development of E-ALD cycle chemistry for the electrodeposition of MoSe2. Those results indicated that acidic HMoO4- and SeO2 precursor solutions would be a better choice for the formation of MoSe2 using E-ALD. Photoelectrochemical (PEC) photovoltage measurements revealed an optical band gap of 1.1 eV for the as-deposited MoSe2 films. Some unreacted MoO2 was detected by the PEC measurements, as well, but were removed by thermal annealing. Some excess elemental Se was also removed during the anneal, and Raman spectroscopy indicated that the films' crystallinity was improved. Deposit quality was followed using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and electron probe microanalysis (EPMA). Se appeared to suppress Mo oxidation and induce MoSe2 film growth in the E-ALD cycle.