ZnSe high temperature radiation detectors

1. Research project:
X-ray induced conductivity of ZnSe and
development of high-temperature detectors of
ionizing radiation
Volodymyr Degoda – Director of R&D Center “Arvina”, Ph.D.
Andrii Sofiienko – Physicist, Ph.D.
1
NATIONAL TARAS SHEVCHENKO
UNIVERSITY OF KYIV
R&D Center “ARVINA”
Kyiv - 2012

2. Table of contents
 General information about ZnSe;
 Methods of the experimental studies;
 Research results;
 Designing and manufacturing of the high-temperature
ZnSe detectors.
2

3. General information about ZnSe
ZnSe is binary diamond-like semiconductor with a band-gap of
2.7 - 2.8 eV at the temperature of 300 K.
ZnSe is used to make optical components (windows, lenses,
prisms and mirrors) for the visible and infrared range (0.5-22 m)
for the optical systems and laser CO2-optics.
ZnSe has a high transmittance value, strength, hardness, optical
uniformity, wide transparency range, erosion and thermal
stability.
3

4. General information about ZnSe
4
Fig. 1 A photo of several ZnSe samples.

5. General information about ZnSe
5
Parameters
Semiconductors
ZnSe CdTe CdZnTe Si Ge GaAs SiC
Eg (300 K), eV 2.80 1.51 1.57 1.11 0.67 1.43 2.86
Тsmelting, 0С 1798 1090 1100 1420 940 1240 2800
ρ, gcm3 5.4 5.9 6.0 2.3 5.3 5.3 --
μе, cm2/V∙s
μh, cm2/V∙s
700
25÷40
1050
100
1000
100
1500
480
4500
1900
8500
450
1200÷800
80÷140
α (300 К), К-1 7.5 4.9 5.0 2.4 5.8 6.0 ≈ 3.0
Radiation
resistance to γ,
Gy
107 < 105 < 106 < 105 < 106 ≈ 3∙105 ≈ 106
Radiation
resistance to n,
1/cm2
1016 < 1013 < 1014 < 1012 < 1014 < 1012 < 1015
The threshold
energy for defect
formation, eV
~ 40 6 ÷ 8 6 ÷ 8 11 ÷ 20 12 ÷ 20 8 ÷ 20 50 ÷ 150
ρR, Оhm∙cm 1011 109 1011 105 104 108 109

6. Methods of the experimental studies
Experimental investigation of the physical characteristics of wide-
gap semiconductors includes:
 Photo-and X-ray induced luminescence;
 Photo- and X-ray induced conductivity;
 Relaxation of the current and phosphorescence;
 Thermally stimulated luminescence and conductivity.
In general, more than 10 techniques were used to study the
physical properties of ZnSe semiconductor in the temperature
range from -265 0C up to +300 0C.
6

7. Methods of the experimental studies
Fig. 2 A schematic of the experimental set-up used for the investigation of ZnSe.
7

8. Research results
8
Fig. 3 Sketch of the experimental set-up adopted for the characterization of X-ray
induced conductivity of ZnSe samples (U0 = 0-1500 V; d = 2-5 mm)
Since X-ray radiation was used as an exciting radiation which is
absorbed completely in the thickness of ZnSe about 80 μm (ЕX = 20
keV), the specific geometry of metal electrodes on the sample surface
was selected as it is shown in Fig. 3. The area between electrodes was
uniformly irradiated with X-rays.

9. Research results
9
Fig. 4 Test sample of monocrystalline ZnSe (used for the testing and investigation
in the cryostat)

10. Research results
10
0 50 100 150 200 250
10
0
10
1
10
2
10
3
10
4
10
5
up to 1000 times
E ~ 1.0 eV
single crystal
E ~ 0.82 eV
polycrystal
Intrinsicconductivity,pA
T,
0
C
1
2
Fig. 5 Temperature dependencies of intrinsic (dark) conductivity of one
polycrystalline ZnSe (1) and one monocrystalline ZnSe (2), Е0 = 400 V/cm

11. Research results
11
-50 0 50 100 150 200 250 300
10
-12
10
-11
10
-10
10
-9
10
-8
10
-7
10
-6
10
-5
Current,A
T,
0
C
10
3
times10
5
times
1, X-ray conductivity (~ 300 Gy/h)
2, intrinsic conductivity
Temperature stabilization of
X-ray conductivity
Fig. 6 Temperature dependencies of X-ray conductivity of single-crystal ZnSe (1)
and intrinsic (dark) conductivity (2), Е0 = 400 V/cm
~ 200 pA at 150 0C

12. Research results
12
Fig. 7 Temperature dependence of X-ray induced conductivity of ZnSe sensor, E0
= 1600 V/cm
Insignificant change of the sensitivity of
ZnSe detectors to X-rays at the heating up
to 200 0C is a prerequisite to use ZnSe as
a high-temperature X-ray detector.

13. Research results
13
0.0 2.0x10
3
4.0x10
3
6.0x10
3
8.0x10
3
1.0x10
4
0.00
0.06
0.12
0.18
0.24
0.30
0.36 i(600 V) D
1.36
i(400 V) D
1.60
D, Gy/h
IX
(D),A
1
2
3
i(200 V) D
1.75
Fig. 8 Dose dependencies of X-ray induced conductivity of single-
crystal ZnSe: U = 200V (1), U = 400V (2), U = 600V (3)

14. Designing and manufacturing of ZnSe detectors
Following requirements should be considered for the designing
of high-temperature ZnSe detectors:
 high optical quality of the crystals;
 minimum intrinsic (dark) conductivity;
 wide operating temperature range up to 200 0C without
cooling;
 high absorption efficiency to ionizing radiation.
14

15. Designing and manufacturing of ZnSe detectors
15
Fig. 9 One polished ZnSe crystal developed for the gamma-ray detector
(10 x 15 x 40 mm)

16. Control of the optical quality
16
Fig. 10 Measuring of the light absorption with use a green semiconductor laser.
µ < 0.1 cm-1
Absorption of the
green light (650 nm)

17. Design and manufacturing of ZnSe detectors
17
Fig. 11 A system of vacuum deposition VUP-5 used for vacuum deposition of
multi-layered metal electrodes on ZnSe crystals.

18. Design and manufacturing of ZnSe detectors
18
Fig. 12 ZnSe multi-electrode integral detector with automatic compensation of
intrinsic (dark) conductivity
For the detection of strong X-
ray flux in the range up to
200 keV a special ZnSe
detector can be developed
with automatic compensation
of the intrinsic (dark)
conductivity.

19. Design and manufacturing of ZnSe detectors
19
Fig. 13 Absorption efficiency of ZnSe to X-ray and gamma radiation at
different thicknesses.

20. Design and manufacturing of ZnSe detectors
20
Fig. 14 A schematic of the measuring system developed for isotopic thickness
gauges utilized strong sources of X-ray or gamma radiation.
An example of the measuring
system for isotopic / X-ray
thickness gauges utilized
strong sources for the greater
range of the measured
thickness.
Operating temperature range:
-40 0C to +200 0C

21. Multielectrode detectors for X-ray thickness gauges
21
Fig. 15 Several samples of multielectrode detectors based on the
monocrystalline undoped ZnSe
Multielectrode ZnSe detectors were developed for the measuring of
the thickness profile of the metal sheet during the hot rolling (R&D
Center “ARVINA”).

22. Multielectrode detectors for X-ray thickness gauges
22
Fig. 16 A schematic of the experimental set-up used for the testing and verification
of ZnSe multielectrode detectors.
Special equipment and methods are necessary for the testing and
verification of ZnSe multielectrode detectors.

23. CONCLUSIONS
23
Undoped monocrystalline ZnSe has extremely low intrinsic
conductivity in wide temperature range from +10 0С up to +200 0С and
small decreasing of X-ray conductivity. This feature can be used for the
designing and manufacturing of X-ray radiation detectors for the
following applications:
 Radiation thickness gauges for hot rolling which are widely used
in the metallurgy;
 Emergency control in the confinement of Nuclear power plant;
 Detecting of high-energy particles (High-energy physics
applications).

24. 24
R&D Center “ARVINA”, Kyiv, Ukraine
(R&D center was founded at the National
Taras Shevchenko University of Kyiv)
Director:
Ph.D.
Degoda Volodymyr Yakovych
01033, Ukraine, Kyiv, Saksaganskogo str., 31,
E-mail: degoda@univ.kiev.ua
Contact information: