AVS 46th International Symposium
    Surface Science Division Friday Sessions
       Session SS2-FrM

Paper SS2-FrM3
STM Tip Induced 1D Chains on H-covered Ni(100) Surface

Friday, October 29, 1999, 9:00 am, Room 607

Session: Adsorption on Metals and Silicon
Presenter: T. Komeda, The Institute of Physical and Chemical Research (RIKEN), Japan
Authors: T. Komeda, The Institute of Physical and Chemical Research (RIKEN), Japan
M. Kawai, The Institute of Physical and Chemical Research (RIKEN), Japan
Correspondent: Click to Email
The adsorption of H on metal surfaces is considered as a weak chemisorption in general, based on its low desorption temperature. Due to its weak bonding, the surface reconstruction on H adsorption is observed only for very open surface, such as (110) surface of fcc transition metal. It has been shown that the H saturated Ni(110) surface at room temperature shows streaky (1x2) superstructure, on which high resolution STM observation showed added and missing rows as the origin of its structure. In this paper, we show STM tip can create very characteristic 1D chains of protrusion and depletion on H-saturated Ni(100) surface; Ni(100) surface is believed to be stable for H adsorption and forms no reconstruction. The 1D structure is apparently similar to the added and missing row structure on H saturated Ni(110) surface. Experimentally clean Ni(100) surface was exposed to 10 L(1L=10-6 torr s) of H2 at 100 K and observed with low temperature STM which is cooled with liquid nitrogen. When the surface is scanned with a very small gap between the tip and the sample (scanning condition such as -1 mV biased on the sample and tunneling current of 4nA), straight protruded rows accompanying depleted rows besides them appear. The height of the protruded row is 0.3-0.5 A, and the high resolution image shows it is composed of a chain of single atoms spaced with 2x1 periodicity. The characteristic 1D structure is similar to the added and missing row structure formed on H saturated Ni(110) surface, and apparently slight touch of the STM tip on the substrate can dig a single row and the released NiH species form added row. As can be seen in the apparent low height of 0.3-0.5 A for the added row on the terrace, the added row and the missing row shows strong bias dependence in the STM image, which indicates very characteristic electronic structures appeared on this quasi 1D structure.