A strong modification of the electronic properties of solution‐processable conjugated polythiophenes by self‐assembled silane molecules is reported. Upon bulk doping with hydrolized fluoroalkyl trichlorosilane, the electrical conductivity of ultrathin polythiophene films increases by up to six orders of magnitude, reaching record values for polythiophenes: (1.1 ± 0.1) × 103 S cm−1 for poly(2,5‐bis(3‐tetradecylthiophen ‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) and 50 ± 20 S cm−1 for poly(3‐hexyl)thiophene (P3HT). Interband optical absorption of the polymers in the doped state is drastically reduced, making these highly conductive films transparent in the visible range. The dopants within the porous polymer matrix are partially crosslinked via a silane self‐polymerization mechanism that makes the samples very stable in vacuum and nonpolar environments. The mechanism of SAM‐induced conductivity is believed to be based on protonic doping by the free silanol groups available within the partially crosslinked SAM network incorporated in the polythiophene structure. The SAM‐doped polythiophenes exhibit an intrinsic sensing effect: a drastic and reversible change in conductivity in response to ambient polar molecules, which is believed to be due to the interaction of the silanol groups with polar analytes. The reported electronic effects point to a new attractive route for doping conjugated polymers with potential applications in transparent conductors and molecular sensors.

The interface formation between HfO2 and H-terminated Si(111) and Si(100) is studied by in situ infrared absorption spectroscopy during atomic layer deposition using alternating tetrakis-ethylmethylamino hafnium (TEMAH) and deuterium oxide (D2O) pulses. The HfO2 growth is initiated by the reaction of TEMAH with Si–H rather than D2O, and there is no evidence for SiO2 formation at moderate growth temperatures (∼100°C). Although Rutherford backscattering shows a linear increase of Hf coverage, direct observations of Si–H, Si–O–Hf, and HfO2 phonons indicate that five cycles are needed to reach the steady state interface composition of ∼50% reacted sites. The formation of interfacial SiO2 (∼0.7nm) is observed after postdeposition annealing at 700°C in ultrapure nitrogen.

Fe-Pt thin-film alloys have been grown by electrodeposition at potentials positive to that required to deposit elemental Fe. X-ray diffraction studies indicate the formation of fine grained face centered cubic alloys, while Rutherford backscattering spectrscopy and energy-dispersive X-ray spectroscopy reveal substantial incorporation of oxygen in the FePt deposits. The Fe-Pt codeposition process is driven by the negative enthalpy associated with alloy formation. The experimentally determined relationship between alloy composition and the iron group underpotential was found to be in reasonable agreement with free energy calculations for the binary alloy system, based on thermochemical data.There is currently considerable interest in FePt as a high-density perpendicular recording medium, due to the high magnetocrystalline anisotropy of the L1 0 phase. The significant challenges of achieving an appropriately oriented L1 0 phase, while maintaining the required grain ͑or particle͒ size of less than 5 nm, remain unsolved, despite considerable effort. 1-3 FePt has attracted additional interest due to its shape-memory properties, and Invar effects, both of potential utility in microelectromechanical systems ͑MEMS͒. 4 In addition to these useful physical properties Fe-Pt and related alloys have potential application as CO-tolerant electrocatalyst in polymer electrolyte fuel cells. 5,6 In all the above applications, process control during synthesis is of central importance.A variety of means have been used to produce Fe-Pt and similar alloys ranging from vacuum methods like MBE and sputtering 2,3,7,8 to electrodepositon 9-13 of thin films or fine particle production by solution phase chemical reduction. 1,14-16 One particular advantage of electrochemical methods is the ability to easily specify and control the supersaturation while monitoring its effect on growth kinetics.Herein we examine the factors affecting alloy composition during electrodeposition from an aqueous electrolyte containing chlorocomplexes of platinum and iron. Traditional alloy deposition studies largely focus on growth in the overpotential domain. 17 In this case, the composition is controlled by the relative rate of reduction of the constituents occurring in a potential regime where both species can be deposited in their elemental form. The desired differential activity, required for a particular alloy composition, is achieved by judicious choice of component concentrations and complex forming ligands. In contrast, in this study the use of the free energy of alloy formation to control alloy composition is demonstrated.The thermodynamic basis for alloy formation is well established. In fact, high temperature electrochemical potential ͑emf͒ measurements have contributed significantly toward the understanding of phase equilibria and the construction of phase diagrams. A necessary condition for binary alloy A 1Ϫx B x formation is equality of the electrochemical potential of the respective constituentswhere E i is the Nernst potential given by ͓2͔The free e...

Molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd) 3 ) is investigated as a p-dopant for organic semiconductors. With an electron affinity of 5.6 eV, Mo(tfd) 3 is a strong oxidizing agent suitable for the oxidation of several hole transport materials (HTMs). Ultraviolet photoemission spectroscopy confirms p-doping of the standard HTM N,. Strong enhancement of hole injection at R-NPD/Au interfaces is achieved via doping-induced formation of a narrow depletion region in the organic semiconductor. Variable-temperature current-voltage measurements on R-NPD: Mo(tfd) 3 (0-3.8 mol %) yield an activation energy for polaron transport that decreases with increasing doping concentration, which is consistent with the effect of the doping-induced filling of traps on hopping transport. Good stability of Mo(tfd) 3 versus diffusion in the R-NPD host matrix is demonstrated by Rutherford backscattering for temperatures up to 110°C. Density functional theory (DFT) calculations are performed to obtain geometries and electronic structures of isolated neutral and anionic Mo(tfd) 3 molecules.

The valence and conduction band densities of states for the HfO 2 / SiO 2 / Si structure are determined by soft x-ray photoemission and inverse photoemission. First principles calculations are used to help in assigning valence band maxima and conduction band minima. The energies of defect states at the band edges are estimated by comparing the theoretical and experimental results. Determinations of the local surface potentials before and after a forming gas anneal are used to help determine the possible location of the charge in the film.

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Single crystal epitaxial Ge1−xSnx alloys with atomic fractions of tin up to x = 0.145 were grown by solid source molecular beam epitaxy on Ge (001) substrates. The Ge1−xSnx alloys formed high quality, coherent, strained layers at growth temperatures below 250 °C, as shown by high resolution X-ray diffraction. The amount of Sn that was on lattice sites, as determined by Rutherford backscattering spectrometry channeling, was found to be above 90% substitutional in all alloys. The degree of strain and the dependence of the effective unstrained bulk lattice constant of Ge1−xSnx alloys versus the composition of Sn have been determined.