Mark C. Hersam

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Femtosecond two-pulse degenerate four-wave mixing spectroscopy was applied to study the exciton dephasing in a broad range of excitation intensities and lattice temperatures. We find that both exciton-exciton and exciton-phonon scattering have profound effects on the dephasing process. The dominant phonon mode involved in the dephasing is identified as the(More)
In the past decade, semiconducting carbon nanotube thin films have been recognized as contending materials for wide-ranging applications in electronics, energy, and sensing. In particular, improvements in large-area flexible electronics have been achieved through independent advances in postgrowth processing to resolve metallic versus semiconducting carbon(More)
We studied the local optical response of semiconducting single-walled carbon nanotubes to wrapping by DNA segments using high resolution tip-enhanced near-field microscopy. Photoluminescence (PL) near-field images of single nanotubes reveal large DNA-wrapping-induced red shifts of the exciton energy that are two times higher than indicated by spatially(More)
With an eye toward using surface morphology to enhance heterogeneous catalysis, Pt nanoparticles are grown by atomic layer deposition (ALD) on the surfaces of SrTiO(3) nanocubes. The size, dispersion, and chemical state of the Pt nanoparticles are controlled by the number of ALD growth cycles. The SrTiO(3) nanocubes average 60 nm on a side with {001} faces.(More)
We observe localization of excitons in semiconducting single-walled carbon nanotubes at room temperature using high-resolution near-field photoluminescence (PL) microscopy. Localization is the result of spatially confined exciton energy minima with depths of more than 15 meV connected to lateral energy gradients exceeding 2 meV/nm as evidenced by(More)
We present a computational investigation into the line shapes of peaks in conductance histograms, finding that they possess high information content. In particular, the histogram peak associated with conduction through a single molecule elucidates the electron transport mechanism and is generally well-described by beta distributions. A statistical analysis(More)
Direct conversion of light into mechanical work, known as the photomechanical effect, is an emerging field of research, largely driven by the development of novel molecular and polymeric material systems. However, the fundamental impediment is that the previously explored materials and structures do not simultaneously offer fast and wavelength-selective(More)
Ubiquitous low-frequency 1/f noise can be a limiting factor in the performance and application of nanoscale devices. Here, we quantitatively investigate low-frequency electronic noise in single-layer transition metal dichalcogenide MoS2 field-effect transistors. The measured 1/f noise can be explained by an empirical formulation of mobility fluctuations(More)
a r t i c l e i n f o Epitaxial graphene, grown by thermal decomposition of the SiC (0001) surface, is a promising material for future applications due to its unique and superlative electronic properties. However, the innate chemical passivity of graphene presents challenges for integration with other materials for device applications. Here, we present(More)