Chemistry Reference
In-Depth Information
Chapter 3
Experiments
Abstract I describe experimental details in this chapter. All experiments were
conducted under ultra-high vacuum (UHV) conditions. In general, since single-
crystalline surfaces of semiconductor and metal are very reactive, they are readily
contaminated by H
2
O, O
2
, etc. in atmospheric conditions. Therefore, UHV con-
ditions (\10
-10
Torr) are essential to avoid contaminations from such gases and
keep well-defined conditions at the atomic level. Principle and technical details of
UHV can be found in some practical topics [
1
-
3
]. A single-crystalline Cu(110)
surface was used as an atomically well-defined template throughout this thesis. As
described in the previous chapter, the structure of water layer on metal surfaces is
determined by the competition between water-water and water-substrate interac-
tions. In this context, a Cu(110) surface is quite unique because several unusual
structures, including a one-dimensional chain [
4
,
5
], an intact two-dimensional
network [
6
], and some partially dissociated overlayers [
7
-
9
] are formed. This
feature is presumably attributed to the quasi one-dimensional atomic arrangement
of Cu(110). The experimental set up, sample preparation, and STM measurement
are summarized in
Sects. 3.1
,
3.2
, and
3.3
, respectively. Additionally, I focus on
the time-resolved measurement using STM in
Sect. 3.4
.
Keywords Ultra-high vacuum conditions
Low temperature
Single crystalline
surfaces
A Cu(110) surface
Scanning tunneling microscope
3.1 Experimental Apparatus
The basic set-up of the STM is shown in Fig.
3.1
. There are two separated chambers
for preparing a single-crystalline surface and for STM measurement at low-
temperature. The tall part in the STM chamber is a refrigeration tank (cryostat).
Temperature of 78 and 6 K can be achieved by filling the cryostat with liquid N
2
