Deposition of Pd Nanoparticles on InP by Electrophoresis: Dependence on Electrode Polarity

Abstract

Layers of nanoparticles deposited onto n-type InP single crystals were prepared by electrophoresis from colloid solutions with reverse micelles-containing Pd nanoparticles. Pd nanoparticles in colloid solutions were monitored by transmission electron microscopy and by optical absorption of Pd surface plasmons. Two types of layers were prepared by electrophoresis with an InP wafer placed on the positive electrode or on the negative electrode, respectively. The layers showed a large distinctness between conductivities in axial and lateral direction. The layers were studied by secondary ions mass spectroscopy and atomic force microscopy. It was shown that only the layers deposited on the positive electrode contained Pd nanoparticles. Diodes were prepared on InP wafers with both types of deposited layers, and their current-voltage characteristics and admittance-frequency characteristics were studied at room temperature. Diodes-containing Pd nanoparticles providing large values of Schottky barrier height 0.856 eV appear to be suitable for making sensitive sensors of hydrogen gas in the air.

Electrophoretic deposition of reverse micelle metal nanoparticles

“…1. The peak at 420 nm is due to surface plasmons in Ag nanoparticles and the peak at 236 nm is due to the AOT surfactant [8]. Similar spectrum has been observed in the colloid solution with Pd showing the peak due to surface plasmons in Pd nanoparticles at 280 nm [8].…”

“…We have also tested the diodes for their sensitivity on hydrogen. The results of the measurements and testing have been shown in our previous papers [7,8,12]. Diodes with Pd nanoparticles deposited with the A type polarity showed a significant sensitivity on the hydrogen-nitrogen mixture while those deposited with the C type polarity showed the sensitivity of one or two orders of magnitude smaller.…”

“…Further research in this direction is needed as electrophoretic deposition is gaining increasing interest as a processing technique for production of nanometer scaled layers [6]. We have reported the deposition of Pd nanoparticles coated in reverse micelles by electrophoresis from colloid solutions in isooctane on InP surface acting as a positive electrode [7,8]. The reverse micelles were formed by sodium bis-(2-ethylhexyl) sulfoccinate (AOT).…”

“…Two polarities of the applied electric potential were used: type A -sample on the anode (electrode with the positive potential) and type C -sample on the cathode (electrode with the negative potential). It has been reported that Pd nanoparticles are deposited with the potential polarity type A [8]. The deposited layers were characterized by SIMS, AFM, optical absorption or reflection spectroscopy, spectroscopic photoluminescence (PL) topography at room and liquid nitrogen temperature and by PL spectroscopy at liquid helium temperature.…”

“…The peak at 420 nm is due to surface plasmons in Ag nanoparticles and the peak at 236 nm is due to the AOT surfactant [8]. Similar spectrum has been observed in the colloid solution with Pd showing the peak due to surface plasmons in Pd nanoparticles at 280 nm [8]. Now we are going to show that Ag nanoparticles are deposited with the potential polarity type C. Optical absorption band due to surface plasmons of Ag nanoparticles deposited on the glass substrate by electrophoresis with the C type polarity is seen in Fig.…”