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'HWDLOV Contents List of Symbols List of Figures List of Tables

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$EVWUDFW  'HWHFWRUVDQGWKHLU&KDUDFWHULVWLFV 1.1 Introduction 1.1.1 Track Detector 1.1.2 Electronic Detectors 1.1.2.1 Semiconductor Detectors 1. Surface Barrier Detector 2.Diffused Junction Detectors 3. Lithium Drifted Junction Detectors 4. High Purity Germanium Detectors 5. Planar Structure 6. Schottky Structure

1.2 Advantages of semiconductor detectors 1.3 Applications of CdTe Detectors 1. Spectrometer i. Uranium and spent Fuel ii. Classification of Plutonium as weapons Grade iii. Chemical Analysis 2. Safeguard Systems 3. Dosimetry 4. Space and Astrophysics 5. Medical Applications 6. Industrial Applications 1.4 Applications of CdZnTe Detectors (Imaging Applications) 1 .5 Literature review 1.6 Aim of the work

         

             



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2.1. Group II-VI Compounds 2.1.1.The Zinc Blend Structure(CadmiumTelluride) (CdTe) 2.1.2 Cadmium Zinc Telluride (CdZnTe) 2.1.3 Diluted Magnetic Semiconductors (DMS) 2.2 Growth Methods 2.2.1 Basic Bridgman method 2.2.2 High Pressure Bridgman (HPB) 2.2.3 Low Pressure Bridgman (LPB) 2.2.4 Physical Vapor Transport (PVT) 2.3 Detection Parameters 2.4 Radiation Defects in Semiconductor Detectors 2.5 Electrical properties of Semiconductor 2.5.1 Resistivity 2.5.2 Mobility 2.5.3 Metal Semiconductor Contacts 2.6 Device Design 2.7 Problems of Design 2.8 Interaction of Radiation with Semiconductor Radiation Detectors 2.9 Nuclear Properties of CdTe & CdMnTe Semiconductor Radiation Detectors 2.9.1 Energy Resolution 2.9.2 Efficiency 2.9.3 Noise 2.9.4 The relation between the mobility lifetime product with the energy 2.9.5 Charge Collection Efficiency 2.9.6 Output Pulse Height 2.9.7 Quality Factor



        

                

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3.1 The Raw Crystal (CdMnTe Material) 3.2 Sample cleaning 3.3 Thin Film and ohmic Contact Preparation 3.4 Sample preparation 1. Planar type detector 2 Schottky type detector 3. MOS device type detector 3.5 Resistivity Measurements 3.6 Hot and Cold Probe Technique 3.7 Annealing 3.8 I-V measurement with Temperature Variation

        

3.9



Detector Test

 5HVXOWVDQG'LVFXVVLRQ 4.1 Testing the Detector 1. Oscilloscope pulse test 2. Multi-Channel Analyzer(MCA) test 4.2 Data Analysis

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5. Conclusions

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List of figures )LJXUH

'HWDLOV

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Chapter One Figure 1-1 Figure 1-2

 

Surface barrier detector Diffused junction detector Lithium drifted junction detector

Figure 1-3 241

1

137





Figure 1-4

Typical

Figure 1-5

The comparison between the energy spectrum of 133Ba rays obtained a) from 2 mm thick planar CdZnTe detector and b) from the first four layers of the stack detector.

Figure 2-1

Ohmic contact properties



Figure 2-2

Schematic presentation of trap levels within forbidden gap



Figure 2-3

Inactivation of deep electron traps



Figure 3-1 Figure3-2-a Figure3-2-b Figure3-2-c Figure3-3

CdMnTe Material Planar type detector sample Schottky type detector sample MOS device type I-V Characteristic for Planar structure for CdMnTe I-V Characteristic for Schottky structure for (In/CdMnTe/Au) I-V Characteristic for MOS structure for CdMnTe Hot and Cold probe testing technique Variation of Conductivity with (1/T) for CdMnTe(2h) Variation of Conductivity with (1/T) for CdMnTe(5h) Sample holder Circuit used for detector test

Am and

Cs spectra obtained by CdTe detector



Chapter Two

Chapter Three

Figure3-4 Figure3-5 Figure3-6 Figure3-7 Figure3-8 Figure3-9 Figure3-10

           

Chapter Four Figure4-1 Figure4-2-a Figure4-2-b Figure4-3-a Figure4-3-b Figure4-4 Figure4-5-a

Circuit used for pulse test The observed figure for the radioactive source Cs137 brought near the sample The observed figure obtained due to irradiating the sample with Cs137 with large time The observed figure obtained due to irradiating the sample with Am241 The observed figure obtained due to irradiating the sample with Am241 with large time The observed figure for the radioactive sourcesCs137& Am241 brought near the sample Repeating of Fig.4-2-b

      

Figure4-5-b Figure4-6 Figure4-7 Figure4-8 Figure4-9 Figure4-10 Figure4-11

The reproduced Figure of Fig.4-5-a The fitted peak of Fig.4-2-b The fitted peak of Fig.4-2-a The fitted peak of Fig.4-3-a The fitted peak of Fig.4-3-b The fitted peaks of Fig.4-4 The fitted peaks of Fig.4-4 with different channel number

      

List of Tables 7DEOHV

'HWDLOV

Table 1-1

The information's included in the references were given in the article (1.5)

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Chapter One 

Chapter Two Table 2-1

Properties of semiconductor detectors materials



Chapter Four Table 4-1

The information included FWHM, Peak channel, Resolution, Area under peak and Error.



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The aim of the this work was the fabrication and studying the characteristics of a nuclear detector prepared from p-CdMnTe, of conductivity of ~10-4 (:.cm)-1 as grown.

Annealing of the samples (2 and 5 hours) changed the

conductivity to about (10-7) (:.cm)-1, three structures were used, as planar with (Au) ohmic contact on both sides, Second structure as Schottky type structure of In-CdMnTe with (Au) ohmic contact on the back face, and Thirdly MOS device for which the samples annealed under oxygen flow for (2h) at 700 Cq. These later samples, were only signals

on

the

successful

samples

that

produced

J-ray

MCA. All other samples failed to do so. These samples

when connected to conventional nuclear spectroscopy electronics, gave reasonable but not high quality s ignals due to irradiating with 137

( Cs+

137

Cs,

241

Am and

241

Am). Matlab-software based on numerical methods were used to

analyze the data. Resolution through (Full Width at Half Maximum), area under the peak and error for this detector were presented. The mobility lifetime product of both electrons and holes for CdMnTe plotted against various gamma energy sources, and then compared with respect to CdZnTe; So there was a clear increase for CdMnTe than CdZnTe.Calculations of transit time, for electrons and holes in CdMnTe, plotted against (1/V) which gave a decrease of the transit time with voltage increase.

The quality factor value has been

calculated for CdMnTe detector and compared to those of CdZnTe and CdTe detectors only at room temperature. The value of quality factor for CdMnTe detector was higher than the others. Calculations of activation energies of annealed CdMnTe samples for 2 and 5 hours under vacuum (10-5torr) gave 0.361 and 0.270 eV respectively.

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Figure 1-2 : Diffused Junction Detector

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FWHM =4.2 keV  Figure 1-4 : Typical

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by CdTe detector [Niraula et al.,1999]   Figure 1-4 : Typical

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Cs spectra obtained

by CdTe detector [Niraula et al.,1999]

  

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V(volt)  Figure 3-5: I-V characteristic for MOS structure for CdMnTe  

  

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 Figure 3-7: Variation of Conductivity with (1/T) for CdMnTe (2h)    



  Figure 3-8: Variation of Conductivity with (1/T) for CdMnTe (5h)                 

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Figure 4-2a: The observed figure for the radioactive source 137Cs brought near the sample(t=59 sec)

  





     

Figure4-2b: The observed figure obtained due to irradiating the sample with 137Cs with long time(t=120 sec).

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Figure 4-3a: The observed figure obtained due to irradiating the sample with 241 Am.

Figure 4-3b: The observed figure obtained due to irradiating the sample with 241 Am with longer time.

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Figure 4-5a: Repeating of Fig. 4-2b.

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Figure 4-7: The fitted peak Fig. 4-2b .

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Figure 4-9 : The fitted peak of Fig. 4-3b



Figure 4-10:The fitted peaks of Fig.4-4   



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Channel

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5. Conclusions 'XH WR WKH IDFW WKDW WKH DYDLODELOLW\ RI HTXLSPHQW DW RXU GLVSRVDOKDYHEHHQGUDPDWLFDOO\UHGXFHGGXHWRHYHQWVRI WKH SUHSDUDWLRQ RI D ODUJH QXPEHU RI VDPSOHV RI &G0Q7H GHWHFWRUKDVEHHQJUHDWO\KLQGHUHG(YHQVRIHZVDPSOHVKDYH EHHQSUHSDUHGDQGWHVWHG )URPDOOWHVWVFDUULHGRXWWKHIROORZLQJFDQEHFRQFOXGHG 1.

CdMnTe detector samples have been prepared in our lab. Even with low quality equipment.

2.

These samples have been tested and proved to give clear Oscilloscope pulses.

3. These samples when connected to conventional nuclear spectroscopy electronics, gave reasonable but not high quality spectra when samples are irradiated with

137

Cs, 241 Am and (137 Cs+ 241 Am).

4. Mathlab based numerical methods are used to analyze these spectra in 3 above.

5. Resolution through (Full Width at Half Maximum) (FWHM), area under the peak and error data for this detector are presented. Our results are in reasonable a agreement with those of [Cavallini et al., 2000].

6. Comparing values of (PW)eh product for electrons and holes plotted against various energy gamma-sources for CdMnTe detector with CdZnTe shows that CdMnTe has large values of (PW)eh than CdZnTe.

7. Calculations of the transit time for charge carriers in CdMnTe, which plotted against (1/V).As the voltage increased, the transit time decrease which means



 the carriers affected highly by the produced electric field within the detector material.

8. From comparison of the quality factor obtained from eq.(2-16) between CdTe, CdZnTe and CdMnTe detectors at room temperature values, such that CdMnTe detector has higher quality factor than CdTe and CdZnTe.

9. Calculations of activation energies for sample of CdMnTe annealed for 2 and 5 hours

under vacuum (10-5 torr) gave values of 0.361 and 0.27eV

respectively.

  



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Arlt R., Gsock K.H. and Rundqusit D.E.,(1992),Proceedings of the Seventh Int. Workshop on R.T.S.C. X and J Ray Detectors, (in Hage-Ali M. and Siffert Paul, (1995) (CdTe Nuclear Detectors And Applications) (Ch.8), (Semiconductors and Semimetals), Vol.43, 291, Academic Press, Inc.). $]RR]$$ KWWSZZZPDWKZRUNVFRPPDWODEFHQWUDOILOHH[FKDQJHORDG)LOHGR"REM HFW,G  REMHFW7\SH )LOH  %DLOLQJ