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KBi 6.33 S 10 and K 2 Bi 8 S 13 were synthesized by the direct combination of K 2 S/Bi 2 S 3 at high temperature (>700°C). The reaction of K 2 S/3.3Bi 2 S 3 at 800°C revealed the presence of a new ternary sulfide KBi 6.33 S 10 (I, 92% yield). The shiny, silver polycrystalline material crystallizes in the orthorhombic space group Pnma (No. 62) with a ) 24.05(1) Å, b ) 4.100-(2) Å, c ) 19.44(1) Å, V ) 1917(3) Å 3 , Z ) 4, and d c ) 5.828 g/cm 3 . Data with F o 2 > 3σ(F o 2 ), 862; no. of variables 108, 2θ max 50°. The final R/R w ) 4.3/4.7%. The structure consists of blocks of Bi 2 Te 3 -and CdI 2 -type units that are connected to form a three-dimensional network with K + ions located in the channels that run along the b axis. The same reaction but with a different reactant ratio at 750°C gave the new ternary sulfide K 2 Bi 8 S 13 (II, 94% yield). This compound crystallizes in the monoclinic space group P2 1 /m (No. 11) with a ) 16.818(2) Å, b ) 4.074(5) Å, c ) 17.801(3) Å, ) 90.48(1)°, V ) 1220(2) Å 3 , Z ) 2, and d c ) 5.900 g/cm 3 . Data with F o 2 > 3σ(F o 2 ), 1924; no. of variables 131, 2θ max 50°. The final R/R w ) 7.3/8.2%. The structure of the shiny rodlike crystals is closely related to that of I. As in I, it also consists of Bi 2 Te 3 -and CdI 2 -type fragments that connect to form K + -filled channels. The two potassium atoms and one bismuth atom are disordered over three sites. Electrical conductivity on I show semiconducting behavior with 10 2 S/cm at 300 K. Compound II possesses an electrical conductivity of 10 2 S/cm at 300 K. The optical bandgaps of I and II (0.06-0.24 eV) were estimated by infrared diffuse reflectance measurements. Thermal analysis and thermal conductivity data for I and II are reported. The thermal conductivity of KBi 6.33 S 10 is found to be substantially lower than that of Bi 2 Te 3 . a The estimated standard deviations in the mean bond lengths and the mean bond angles are calculated by the equations σl ) {∑n(lnl) 2 /n(n -1)} 1/2 , where ln is the length (or angle) of the nth bond, l the mean length (or angle), and n the number of bonds.

The rate of base-mediated ester hydrolysis in monolayers of 11-mercaptoundecyl isonicotinate on gold is monitored by infrared spectroscopy and cyclic voltammetry. The hydrolysis product, a surface-confined alcohol, can be converted to a trifluoroacetate, increasing the sensitivity of infrared monitoring. Pentaammineruthenium(II) can be attached to the pendant isonicotinate either prior to or after monolayer assembly, leading to monolayers with a highly-charged monolayer/solution interface and a built-in electrochemical probe. The rate of ester hydrolysis within the monolayer is controlled by steric factors associated with monolayer packing and by the amount of charge at the monolayer/solution interface. The stability of the pendant Ru(III) complex is very sensitive to pH and interfacial charge. These results are correlated with Gouy-Chapman double-layer theory.

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Using surface chemical modification to eliminate the generic problems of high surface recombination velocity and Fermi level pinning is studied on InAs( 100). Raman scattering and X-ray photoelectron spectroscopy (XPS) are used to investigate passivation, provided by alkanethiols, RSH; R = CH3(CH2). both neat and in ethanolic solutions, of this surface against oxidation. The magnitude of the interracial bandbending is obtained by analysis of Raman scattering from the unscreened LO phonon, which arises from the near -surface charge accumulation region (CAR). Removing the native oxide with a Br:CH30H chemomechanical etch reduces the surface band bending, but atmospheric oxidation increases band bending to its original level over several hours.Chemical passivation prevents band-bending for periods up to several weeks. DISCLAIMER DISCLAIMERPortions of this document may be illegible in electronic image products.Images are produced from the best availabie original document. Samples were etched in a 1YO Brz:CHJOH (Br:MeOH) solution for 30s and kept in NL to prevent oxide growth between the etch and passivation steps. Profilometry on stepprofiles determined the etch rate to be 27 + 4~/s . Passivations were carried out in both neat alkanethiol and 1 mM solutions of alkanethiol in deaerated ethanol.The Raman spectrum of InAs exposed to various processing steps is given in Figure 1. The spectrum of the unprocessed sample shows two modes: a low-frequency coupled phonon-plasmon mode, L+ observed near 225 cm-', originating in the bulk of the n+-hu%, and an unscreened LO mode observed at 239 cm-' originating from the CAR as a result of wavevector non-conservation.The narrow width of the CAR is associated with uncertainty in the scattering wavevector: scattering from regions of k-space corresponding to wavelengths smaller than the Thomas-Fermi screening length is observed7. In a series of similarly prepared and processed samples the LO mode intensity can be taken to reflect the spatial extent of the CAR and, by inference, the magnitude of the surface state density pinning the surface Fermi Ievel.zsComparing the spectra before and immediately after etching shows a decrease in the unscreened LO mode intensity. Also shown in Fig. 1 is the result of exposing the freshly etched sample to atmospheric 02 for varying times. Without passivation the LO mode, quenched by etching, is observed to regenerate within a few hours. Figure 2 shows the effect of storing the sample in dry N2, removing the sample only periodically for Raman measurements. A small increase in LO intensity is observed after the first measurement, which subsequently stabilizes. We infer from these observations that exposure to 02 repins the Fermi level above the conduction band. Apparently, surface oxidation plays a more significant role in Fermi level re-pinning than crystal termination and reconstruction.To study the passivation of InAs(100) freshly etched samples were treated with 1 mM ethanolic solutions of alkanethiol: octadecanethiol, n = 17, hexadecanet...