Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Atomic structure of Ge quantum dots on the Si(001) surface   In situ morphological investigation of the {105} faceted Ge islands on the
Si(001) surface (hut clusters) have been carried out using an ultra high vacuum
instrument integrating a high resolution scanning tunnelling microscope and a
molecular beam epitaxy vessel. Both species of hut clusters--pyramids and
wedges--were found to have the same structure of the {105} facets which was
visualized. Structures of vertexes of the pyramidal clusters and ridges of the
wedge-shaped clusters were revealed as well and found to be different. This
allowed us to propose a crystallographic model of the {105} facets as well as
models of the atomic structure of both species of the hut clusters. An
inference is made that transitions between the cluster shapes are impossible.

16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas