Palladium nanoparticles on InP for hydrogen detection

Department of Physical Electronics, Czech Technical University, V Holesovickach 2, Prague, Czeck Republic. .
Nanoscale Research Letters (Impact Factor: 2.78). 06/2011; 6(1):410. DOI: 10.1186/1556-276X-6-410
Source: PubMed


Layers of palladium (Pd) nanoparticles on indium phosphide (InP) were prepared by electrophoretic deposition from the colloid solution of Pd nanoparticles. Layers prepared by an opposite polarity of deposition showed different physical and morphological properties. Particles in solution are separated and, after deposition onto the InP surface, they form small aggregates. The size of the aggregates is dependent on the time of deposition. If the aggregates are small, the layer has no lateral conductance. Forward and reverse I-V characteristics showed a high rectification ratio with a high Schottky barrier height. The response of the structure on the presence of hydrogen was monitored.

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    ABSTRACT: Layers of Pd nanoparticles on n-InP seem to be good structure for monitoring hydrogen concentration in the air. Generally, energetic barrier, called Schottky barrier, is formed on the interface between metal and semiconductor. This barrier is lowered by the presence of hydrogen and this influences the amount of current which flows through the structure. Pd was chosen for its ability to dissociate hydrogen molecules to single atoms. This fact is further enhanced by nanoparticle form of this metal because of its high surface-to-volume ratio. Pd nanoparticles were prepared in colloid solution stabilized by AOT. The layers were prepared by electrophoretic deposition through the mask of polystyrene spheres. Electrophoreticdeposition lies in acceleration of particles in electric field in the direction towards the InP wafer. SEM measurement showed that particles in colloid solution are separated and after deposition they form small aggregates on InP. The size of these aggregates depends on the time of deposition. The I-V characteristics were measured and from these data Schottky barrier height and ideality factor were calculated. The morphology of layers was monitored by SEM.
    01/2011: pages 545-549; , ISBN: 9788087294277
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    ABSTRACT: Large attention has been devoted worldwide to the investigation of hydrogen sensors based on various Schottky diodes. We prepared graphite semimetal Schottky contacts on polished n-InP and n-GaN wafers partly covered with nanoparticles of catalytic metals Pd or Pt by applying colloidal graphite. Metal nanoparticles were deposited electrophoretically from colloids prepared beforehand. Deposited nanoparticles were imaged by scanning electron microscopy, atomic force microscopy, and scanning tunneling microscopy on the as-made and annealed-in-vacuum samples. Current-voltage characteristics of prepared Schottky diodes had very high rectification ratios, better than 107 at 1 V. It was shown that the barrier heights of these diodes were equal to the difference between the electron affinity of InP or GaN and the electron work function of the metal Pd or Pt (Schottky-Mott limit). That was a good precondition for the high sensitivity of the diodes to hydrogen, and indeed, high sensitivity to hydrogen, with the detection limit better than 1 ppm, was proved.
    Nanoscale Research Letters 07/2012; 7(1):415. DOI:10.1186/1556-276X-7-415 · 2.78 Impact Factor