Preparation and characterizations of thalli um bromide single crystal for room
temperature radiation detector use
Dongxiang Zhou, Lin Quan, Xiaoyan Chen, Shijin Yu, Zhiping Zheng, Shuping Gong
Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, PR China
article info
Article history:
Received 18 September 20 08
Received in revised form
11 December 2008
Accepted 15 December 2008
Communicated by M. Schieber
Available online 10 February 2009
PACS:
07.85.Nc
29.40.Wk
73.61.Le
Keywords:
A1. Characterization
A2. Growth from melt
A2. Single crystal growth
B1. Inorganic compounds
B2. Semiconducting materials
abstract
Thallium bromide (TlBr) crystal of 8-mm-diameter, preferentially oriented in [110] direction has been
prepared using a melt-b ased method without mechanical vibrations. Analyses on the crystal quality and
growth process were made based on characterizations of X-ray diffraction, rocking curve, ultraviolet
absorption and transmittance spect rum. Most section of the crystal exhibits crystalline perfection and
low stress, and its bandgap was calculated to be 2.88 eV. Influence of ampoule diameter on crystal
quality has been discussed. Resistivity of the material was measured to be over 10
10
O
cm. Spectroscopic
response of the fabricated detectors to
241
Am shows 59.5 keV peak with the resolution of 38.27%.
& 2009 Elsevier B.V. All rights reserved.
1. Introduction
The selection of detecting material is greatly crucial to the
performances of the radiation detector. Thallium bromide (TlBr)
single crystal is a type of compound semiconductor with wide
bandgap, which enables it to work under room temperature with
low-noise signal. Its high atomic number (Tl: 81, Br: 35) and high
density (7.56 g/cm
3
) benefit it with high detection efficiency [1]
and high stopping power [2]. Furthermore, owing to its simple
cubic crystal structure (CsCl type) and relatively low melting point
(460 1C), it is convenient to grow TlBr crystal by melt-based
method. Defections and imperfections in the single crystal may
degrade performance of the detectors. Therefore, single crystal for
detector use should be of low stress and crystalline perfection.
On account of the excellent physical attributes of TlBr crystal, it
has been researched as a promising room temperature radiation
detector material since 1990. Hitomi et al. [3,4] grew TlBr single
crystal by traveling molten zone (TMZ) method. Owens et al. [5]
utilized vertical Bridgman–Stockbarger method. They have also
tried the hydrothermal method [6], but only small grains with the
size 0.3–3 mm were obtained. The melt-based methods are
relatively mature method [3–8], but mechanical vibrations due
to movement of the heating element or the ampoule were
inevitable in both the Bridgman method and the TMZ method,
which may affect the crystal quality.
In the present work, an 8-mm-diameter TlBr single crystal,
preferentially oriented in [110] direction, was prepared by a novel
melt-based method with no mechanical vibrations. X-ray diffrac-
tion (XRD), X-ray rocking curve, ultraviolet (UV) transmission and
UV absorption spectrum were used to characterize the crystal
quality. To evaluate the crystal as radiation detector, resistivity
and its spectroscopic response to the
241
Am source have been
measured.
2. Experimental procedure
2.1. Crystal growth and characterization
Three ampoules with inner diameters of 8, 10 and 15
m
mwere
utilized, and their products were designated as P1, P2 and P3,
respectively. The ampoules have been previously washed repeat-
edly with de-ionized water before use. Then, commercially
ARTICLE IN PRESS
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journal homepage: www.elsevier.com/locate/jcrysgro
Journal of Crystal Growth
0022-0248/$ - see front matter & 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jcrysgro.2008.12.057
Corresponding author. Tel.: +86 027 87557447; fax: +86 027 87545167.
E-mail address: Lin_Quan_HUST@hotmail.com (S. Gong).
Journal of Crystal Growth 311 (2009) 2524–2529