Localized surface plasmon absorption features arise at high doping levels in semiconductor nanocrystals, appearing in the near-infrared range. Here we show that the surface plasmons of tin-doped indium oxide nanocrystal films can be dynamically and reversibly tuned by postsynthetic electrochemical modulation of the electron concentration. Without ion intercalation and the associated material degradation, we induce a > 1200 nm shift in the plasmon wavelength and a factor of nearly three change in the carrier density.

The manipulation of the bandgap of graphene by various means has stirred great interest for potential applications. Here we show that treatment of graphene with xenon difluoride produces a partially fluorinated graphene (fluorographene) with covalent C-F bonding and local sp(3)-carbon hybridization. The material was characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, electron energy loss spectroscopy, photoluminescence spectroscopy, and near edge X-ray absorption spectroscopy. These results confirm the structural features of the fluorographane with a bandgap of 3.8 eV, close to that calculated for fluorinated single layer graphene, (CF)(n). The material luminesces broadly in the UV and visible light regions, and has optical properties resembling diamond, with both excitonic and direct optical absorption and emission features. These results suggest the use of fluorographane as a new, readily prepared material for electronic, optoelectronic applications, and energy harvesting applications.

In order to explore the similarity and difference between the absorbance calculated by the Mie theory (A Mie ) and the Maxwell-Garnett (MG) effective medium approximation (A MG ), both were calculated using the Drude dielectric function for a range of volume fractions f V and bulk plasma frequencies (ω P ). For each case, the optical path length L was adjusted such that f V * L was kept constant. In this way, the total volume of the absorbing material is kept constant, resulting in comparable absorbance values for all f V . The mean-square-difference (MSD) between A Mie and A MG is shown in Fig. S1.

Analysis of the transmittance and reflectance of transparent conducting oxide thin films and nanocrystal films can be accurately modeled using the Drude free electron theory to extract electrical transport properties if enough care is taken. However, several fits starting from different initial guesses are needed before confidence in the extracted Drude parameters can be obtained. Film thickness, optical carrier concentration, and optical carrier mobility can be reliably derived when using either a fully empirical or semiempirical model for the ionized impurity scattering. The results are in good agreement with those based on more arduous spectroscopic ellipsometry measurements. Furthermore, fitting the reflectance along with the transmittance reduces the uncertainty, but does not significantly affect the values of the extracted parameters.

Pulsed emissive probe techniques have been used to determine the plasma potential distribution of high power impulse magnetron sputtering (HiPIMS) discharges. An unbalanced magnetron with a niobium target in argon was investigated for pulse length of 100 µs at a pulse repetition rate of 100 Hz, giving a peak current of 170 A. The probe data were taken with a time resolution of 20 ns and a spatial resolution of 1 mm. It is shown that the local plasma potential varies greatly in space and time. The lowest potential was found over the target's racetrack, gradually reaching anode potential (ground) several centimeters away from the target. The magnetic pre-sheath exhibits a funnel-shaped plasma potential resulting in an electric field which accelerates ions toward the racetrack. In certain regions and times, the potential exhibits weak local maxima which allow for ion acceleration to the substrate. Knowledge of the local E and static B fields lets us derive the electrons' E × B drift velocity, which is about 10 5 m/s and shows structures in space and time.

Abstract. Due to their high intrinsic electron mobility, CdO-based materials are gaining interest as transparent conductive oxides. By creating model dielectric functions based on the Drude theory, accurate fits to the measured transmittance and reflectance of CdO and CdO:In thin-films were achieved without using a frequency dependent Drude damping parameter. Difference in the model between undoped and In-doped CdO showed that the Burstein-Moss shift is not the only mechanism which improves the transparency in In-doped samples. Comparing the Drude analysis with Hall measurements revealed a nonlinear relationship between the free-electron effective mass and the carrier concentration, an effect which is caused by the nonparabolicity of the CdO conduction band. Analysis of 50 CdO:In thin-films grown by pulsed filtered cathodic arc showed the nonparabolicity factor was C = (0.5 ± 0.2) eV −1 and the band-edge effective mass was (0.16 ± 0.05)me. Knowledge of the effective mass allows for optical measurements of carrier mobility, which was less than or equal to the Hall measured mobility in these films due to the large electron mean-free-path compared to the grain size.

chemical, biochemical, and even biological species ( Figure 1 ). Furthermore, their distinctive near-infrared (NIR) optical response can be quantitatively interpreted [ 14,15 ] so that these redox processes can be tracked with single-electron sensitivity. To demonstrate their exciting new properties in interrogating complex redox systems, we use them to quantify chemically driven charge transfer across the electrifi ed cell membranes of Shewanella oneidensis MR-1, requiring only a simple optical readout and absent any external electrodes. Results and DiscussionRecently, it was shown that the characteristic wavelength and intensity of the NIR plasmon resonance absorption of tin-doped indium oxide (ITO) nanocrystals bound to an electrode can be strongly modulated in a reversible manner using a directional voltage bias. [ 9,16 ] These changes arise from the dependence of the Electron transfer in complex aqueous systems can be observed remotely with single-electron sensitivity using locally dispersed nanostructures conferred with electronic charge concentration-dependent plasmonic properties. When introduced to a system out of redox equilibrium, tin-doped indium oxide nanocrystals undergo rapid multielectron transfer until redox equilibrium is reached; this modulates their free carrier concentration and plasmonic optical properties in the spectrally isolated near-infrared. This capability is harnessed here to noninvasively track, model, and quantify electron transfer events reversibly for organic, inorganic, biogenic, and even living cells.Adv. Optical Mater. 2015, 3, 1293-1300 www.MaterialsViews.com www.advopticalmat.de Figure 1. Plasmonic doped metal oxide nanocrystals reversibly exchange electrons with redox-active small molecules, biomacromolecules, and live bacteria. These multi-electron exchanges modulate their free-carrier concentration, thus changing their plasmonic optical properties. This redoxresponsive plasmon absorbance can be modeled to provide quantitative analysis of electron transfer in systems out of redox equilibrium. wileyonlinelibrary.com

Deliberately oxidized iridium, platinum, and palladium Schottky contacts were fabricated on the Zn-polar and O-polar faces of hydrothermal bulk ZnO by eclipse pulsed laser deposition in an oxygen ambient. The barrier heights of these oxidized contacts were significantly higher than their plain metal counterparts, with ideality factors approaching the image-force-controlled limit for laterally homogeneous interfaces. The key aspects of this technique are a low deposition energy and the use of an oxidizing environment which reduces interfacial defects, particularly oxygen vacancies. In each case, the barriers on the Zn-polar face were 210–260 meV higher than those on the O-polar face.