John P. Ziegler

Photoelectron spectroscopy studies of the hydrogenation of cyanogen on Pt(111): Comparison with HCN and ethylenediamine

Abstract X-ray photoelectron spectra as a function of anneal temperature are used to compare the thermally initiated chemistry of C2N2 + H2 on Pt(111) with that of C2N2, HCN and ethylenediamine. These spectra show that the product of the reaction of C2N2 with coadsorbed hydrogen (the γ state of C2N2 + H2/Pt(111)) is not HCN but is more likely to be a surface di-imine species. The N1s binding energy of this partially hydrogenated species is ∼ 399.3 eV. HCN adsorption on Pt(111) leads to two distinct chemical species with N1s binding energies of 398.6 and 396.9 eV which are interpreted in terms of molecular and dissociative adsorption respectively.

The interface chemistry of HgCdTe passivated with native sulfide layers grown from nonaqueous and aqueous polysulfide solutions

We have grown anodic sulfide passivation layers on HgCdTe from both nonaqueous and aqueous polysulfide solutions. In both cases CdS layers are nominally obtained. The growth behavior of the sulfide layers is found to be quite different in the different electrolytes. Capacitance–voltage measurements on metal‐insulator semiconductor device structures that incorporated a ZnS cap and Pd gate metal over the CdS have been used to compare the electrical properties of the interfaces produced. Preliminary evidence suggests that aqueous anodic sulfide layers may be more stable than nonaqueous ones, but contain more positive fixed charge and mobile ion charge. Auger electron spectroscopy depth profiles indicate that the aqueous anodic sulfides are oxide free, but appear to contain more Hg and Te contamination than nonaqueous anodic sulfides.

Aqueous electrochemical growth of anodic sulfide films on mercury cadmium telluride

We present here the first demonstration that oxide‐free anodic sulfide layers can be grown on HgCdTe from aqueous electrolytic solutions. Previous work has shown that anodic sulfide films grown from nonaqueous solutions have great potential as passivating layers for HgCdTe. In this work Auger electron spectroscopy depth profiles are used to show that little or no oxide is left at the HgCdTe/CdS interface even when an aqueous growth electrolyte is utilized. Capacitance‐voltage data on metal‐insulator‐semiconductor structures show that the temperature stability of the aqueous sulfide films may be superior to those grown from nonaqueous electrolytes.

Passivation of HgCdTe with CdS thin films: Correlation of device characteristics with surface spectroscopy

We present results on the passivation of HgCdTe with thin films of CdS grown anodically from nonaqueous polysulfide electrolytes. Electrochemical measurements have been carried out to develop an understanding of the film growth. Capacitance‐voltage measurements on metal‐insulator‐semiconductor (MIS) device structures that incorporated a ZnS cap and Pd gate metal over the CdS are used to compare electrical properties of the interface with Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS) depth profiles. The surface spectroscopies were carried out using a sample temperature of 170 K, which allowed us to easily observe Hg by Auger electron spectroscopy. XPS and AES results show that Hg and Te are partially incorporated into the CdS layer, as sulfides that did not completely dissolve during the film growth. The interdiffusion of Zn into the interface resulted in large hysteresis in the C‐V data. By minimizing the Zn interdiffusion, MIS devices with low hysteresis (∼0.25 V) that are ...

Polycrystalline n‐SrTiO3 as an electrode for the photoelectrochromic switching of Prussian blue films

We have developed methods for the preparation of polycrystalline n‐SrTiO3 electrodes which show low dark currents and reasonable efficiencies for photoelectrochromic switching of Prussian blue films. Electrochemical methods were used to characterize the polycrystalline electrodes and the Prussian blue films. The Prussian blue→Prussian white charge‐transfer reaction occurs via a state within the SrTiO3 band gap, located at ∼−0.68 V (versus saturated calomel electrode), the same as that measured on single‐crystal n‐SrTiO3 electrodes. Good image contrast and stability are demonstrated with these polycrystalline electrodes.