A facile room-temperature electrochemical deposition process for germanium sulfide (GeS(x)) has been developed with the use of an ionic liquid as an electrolyte. The electrodeposition mechanism follows the induced codeposition of Ge and S precursors in ionic liquids generating GeS(x) films. The electrodeposited GeS(x) films were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and Raman and X-ray photoelectron spectroscopy (XPS). An aqueous-based Ag doping method was used to dope electrochemically grown GeS(x) films with controlled doping compared to the conventional process, which can be used in next-generation solid-state memory devices.

Vibrational sum frequency generation (VSFG) spectroscopy was used to measure the interfacial spectra of fullerene thin films on dielectric substrates that are commonly used in IR spectroscopy. The VSFG spectra on SiO2 and CaF2 exhibit notably different intensities for the F1u and Ag vibrational modes. This difference is attributed to different interfacial surface charges and C60/surface interactions. DFT calculations were performed to model the influence of a unidirectional electrostatic perturbation on the IR and Raman activities. The VSFG activities were then calculated for comparison to the interfacial second-order susceptibilities obtained from multilayer interference fitting of the experimental spectra. We find that the negative surface charge of CaF2 substrates causes a larger perturbation of fullerene than native silica surfaces, which leads to a stronger influence on the VSFG spectra.

Optical interference effects can be a nuisance in spectroscopy, especially in nonlinear experiments in which multiple incoming and outgoing beams are present. Vibrational sum frequency generation is particularly susceptible to interference effects because it is often applied to planar, layered materials, driving many of its practitioners to great lengths to avoid signal generation from multiple interfaces. In this perspective, we take a positive view of this metaphorical "lemon" and demonstrate how optical interference can be used as a tool to extract subtle changes in interfacial vibrational spectra. Specifically, we use small frequency shifts at a buried interface in an organic field-effect transistor to determine the fractional charge per molecule during device operation. The transfer matrix approach to nonlinear signal modeling is general and readily applied to complex layered samples that are increasingly popular in modern studies. More importantly, we show that a failure to consider interference effects can lead to erroneous interpretations of nonlinear data.

Determination of molecular orientation at interfaces by vibrational sum frequency generation spectroscopy (VSFG) requires measurements using at least two different polarization combinations of the incoming visible, IR, and generated SFG beams. We present a new method for the simultaneous collection of different VSFG polarization outputs by use of a modified 4f pulseshaper to create a simple frequency comb. Via the frequency comb, two visible pulses are separated spectrally but aligned in space and time to interact at the sample with mixed polarization IR light. This produces two different VSFG outputs that are separated by their frequencies at the monochromator rather than their polarizations. Spectra were collected from organic thin films with different polarization combinations to show the reliability of the method. The results show that the optical arrangement is immune to fluctuations in laser power, beam pointing, and IR spectral shape.