Despite challenges to control stoichiometry in the vanadium–sulfur system, template-free growth of patrónite, VS4, thin films is demonstrated for the first time. A novel atomic layer deposition (ALD) process enables the growth of phase pure films and the study of electrical and vibrational properties of the quasi-one-dimensional (1D) transition metal sulfide. Self-limiting surface chemistry during ALD of VS4 is established via in situ quartz crystal microbalance and quadrupole mass spectrometry between 150 and 200 °C. The V precursor, unconventionally, sheds all organic components in the first half-cycle, while the H2S half-cycle generates the disulfide dimer moiety, S2 –2, and oxidizes V3+ to V4+. X-ray analysis establishes VS4 crystallinity and phase purity, as well as a self-limiting growth rate of 0.33 Å/cy, modest roughness of 2.4 nm, and expected density of 2.7 g/cm3. Phase pure films enable a new assignment of vibrational modes and corresponding Raman activity of VS4 that is corroborated by density functional theory (DFT) calculations. Finally, at elevated growth temperatures, a change in the surface mechanism provides a synthetic route to a second vanadium–sulfur phase, V2S3.

Atomic layer deposition (ALD) of indium sulfide (In2S3) films was achieved using a newly synthesized indium precursor and hydrogen sulfide. We obtain dense and adherent thin films free from halide and oxygen impurities. Self-limiting half-reactions are demonstrated at temperatures up to 225 °C, where oriented crystalline thin films are obtained without further annealing. Low-temperature growth of 0.89 Å/cycle is observed at 150 °C, while higher growth temperatures gradually reduce the per-cycle growth rate. Rutherford backscattering spectroscopy (RBS) together with depth-profiling Auger electron spectroscopy (AES) reveal a S/In ratio of 1.5 with no detectable carbon, nitrogen, halogen, or oxygen impurities. The resistivity of thin films prior to air exposure decreases with increasing deposition temperature, reaching <1 Ω·cm for films deposited at 225 °C. Hall measurements reveal n-type conductivity due to free electron concentrations up to 10(18) cm(-3) and mobilities of order 1 cm(2)/(V·s). The digital synthesis of In2S3 via ALD at temperatures up to 225 °C may allow high quality thin films to be leveraged in optoelectronic devices including photovoltaic absorbers, buffer layers, and intermediate band materials.

Actively tunable optical transmission through artificial metamaterials holds great promise for next-generation nanophotonic devices and metasurfaces. Plasmonic nanostructures and phase change materials have been extensively studied to this end due to their respective strong interactions with light and tunable dielectric constants under external stimuli. Seamlessly integrating plasmonic components with phase change materials, as demonstrated in the present work, can facilitate phase change by plasmonically enabled light confinement and meanwhile make use of the high sensitivity of plasmon resonances to the variation of dielectric constant associated with the phase change. The hybrid platform here is composed of plasmonic indium-tin-oxide nanorod arrays (ITO-NRAs) conformally coated with an ultrathin layer of a prototypical phase change material, vanadium dioxide (VO), which enables all-optical modulation of the infrared as well as the visible spectral ranges. The interplay between the intrinsic plasmonic nonlinearity of ITO-NRAs and the phase transition induced permittivity change of VO gives rise to spectral and temporal responses that cannot be achieved with individual material components alone.

Substitutional alloys of several thin film semiconductors have been proposed as intermediate band (IB) materials for use in next-generation photovoltaics, which aim to utilize a larger fraction of the solar spectrum without sacrificing significant photovoltage. We demonstrate a novel approach to IB material growth, namely atomic layer deposition (ALD), to allow unique control over substitutional-dopant location and density. Two new ALD processes for vanadium sulfide incorporation are introduced, one of which incorporates a vanadium(III) amidinate previously untested for ALD. Using this process, we synthesize the first thin film V x In (2−x) S 3 intermediate band semiconductors and further demonstrate that the V:In ratio, and therefore intraband gap density of states, can be finely tuned according to the ALD dosing schedule. Deposition on a crystalline In 2 S 3 underlayer promotes the growth of a tetragonal β-In 2 S 3 -like phase V x In (2−x) S 3 , which exhibits a distinct sub-band gap absorption peak with onset near 1.1 eV in agreement with computational predictions. However, the V x In (2−x) S 3 films lack the lower-energy transition predicted for a partially filled IB, and photoelectrochemical devices reveal a photocurrent response only from illumination with energy sufficient to span the parent band gap.