CN116334764A - Method for inhibiting tellurium-rich inclusion defects in CZT crystal and improving resistivity of CZT crystal - Google Patents
Method for inhibiting tellurium-rich inclusion defects in CZT crystal and improving resistivity of CZT crystal Download PDFInfo
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- 239000013078 crystal Substances 0.000 title claims abstract description 96
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 title claims abstract description 74
- 229910052714 tellurium Inorganic materials 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 47
- 230000007547 defect Effects 0.000 title claims abstract description 20
- 230000002401 inhibitory effect Effects 0.000 title claims abstract description 14
- 239000010453 quartz Substances 0.000 claims abstract description 80
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 80
- 238000000137 annealing Methods 0.000 claims abstract description 63
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 46
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910052738 indium Inorganic materials 0.000 claims abstract description 30
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 21
- 230000001681 protective effect Effects 0.000 claims abstract description 3
- 239000007789 gas Substances 0.000 claims description 28
- 238000004321 preservation Methods 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 14
- 238000005498 polishing Methods 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 5
- 238000000227 grinding Methods 0.000 claims description 5
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 4
- 238000000605 extraction Methods 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 238000004506 ultrasonic cleaning Methods 0.000 claims description 2
- MYBLAOJMRYYKMS-RTRLPJTCSA-N 1-(2-chloroethyl)-1-nitroso-3-[(3r,4r,5s,6r)-2,4,5-trihydroxy-6-(hydroxymethyl)oxan-3-yl]urea Chemical compound OC[C@H]1OC(O)[C@H](NC(=O)N(CCCl)N=O)[C@@H](O)[C@@H]1O MYBLAOJMRYYKMS-RTRLPJTCSA-N 0.000 claims 16
- 229910052793 cadmium Inorganic materials 0.000 abstract description 9
- 239000012535 impurity Substances 0.000 abstract description 6
- 238000002844 melting Methods 0.000 abstract description 5
- 230000008018 melting Effects 0.000 abstract description 5
- 230000008569 process Effects 0.000 abstract description 5
- 230000004048 modification Effects 0.000 abstract description 3
- 238000012986 modification Methods 0.000 abstract description 3
- 238000009792 diffusion process Methods 0.000 abstract description 2
- 238000003466 welding Methods 0.000 abstract description 2
- QWUZMTJBRUASOW-UHFFFAOYSA-N cadmium tellanylidenezinc Chemical compound [Zn].[Cd].[Te] QWUZMTJBRUASOW-UHFFFAOYSA-N 0.000 description 55
- 238000009413 insulation Methods 0.000 description 12
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 7
- 239000012071 phase Substances 0.000 description 7
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 4
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
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- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 4
- 238000004140 cleaning Methods 0.000 description 4
- 229910021642 ultra pure water Inorganic materials 0.000 description 4
- 239000012498 ultrapure water Substances 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- OEDMOCYNWLHUDP-UHFFFAOYSA-N bromomethanol Chemical compound OCBr OEDMOCYNWLHUDP-UHFFFAOYSA-N 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 229910052950 sphalerite Inorganic materials 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910001297 Zn alloy Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- CEKJAYFBQARQNG-UHFFFAOYSA-N cadmium zinc Chemical compound [Zn].[Cd] CEKJAYFBQARQNG-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000002059 diagnostic imaging Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
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- 238000010587 phase diagram Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
- C30B33/02—Heat treatment
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/46—Sulfur-, selenium- or tellurium-containing compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Chemical & Material Sciences (AREA)
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- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
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Abstract
The invention belongs to the field of CZT crystal modification, and discloses a method for inhibiting tellurium-rich inclusion defects in CZT crystals and improving resistivity of the CZT crystals. According to the annealing method, a horizontal annealing furnace with independent control of double temperature areas and open tube annealing are combined, indium and tellurium are used as annealing sources, the temperature higher than the melting point of tellurium-rich impurities is used as annealing temperature, nitrogen is used as protective atmosphere, annealing and element diffusion doping treatment of tellurium-zinc-cadmium crystals are completed in one step, and the purposes of inhibiting tellurium-rich impurities in the crystals and improving the resistivity of the tellurium-zinc-cadmium crystals are achieved in a short annealing time. The invention has the advantages of no need of tube welding treatment, few operation procedures, repeated utilization of the quartz tube, short annealing period, avoiding of complex annealing process by a two-step method, high efficiency and low cost, and is a more practical annealing method.
Description
Technical Field
The invention belongs to the field of CZT crystal modification, and particularly relates to a method for inhibiting tellurium-rich inclusion defects in a CZT crystal and improving the resistivity of the CZT crystal.
Background
Cadmium Zinc Telluride (CZT) is a group II-VI compound semiconductor having a sphalerite type face-centered cubic structure that has evolved from cadmium telluride (CdTe) crystals. Because of the excellent photoelectric property of CZT crystals, nuclear radiation detectors prepared according to the CZT crystals are widely applied to the fields of astrophysics, safety detection, environment detection, medical imaging, industrial control and the like. However, the CZT crystal has high growth temperature, low thermal conductivity and easy formation of a concave growth interface which is unfavorable for crystal growth, so that tellurium-rich melt with the front edge deviating from the stoichiometric ratio of the growth interface is wrapped by the concave growth interface, thereby forming tellurium-rich inclusions and jeopardizing the photoelectric property of the CZT crystal; cadmium components in CZT have high equilibrium vapor pressure, and cadmium is easy to volatilize in the growth process of the CZT crystal, so that a large number of cadmium vacancies exist in the grown crystal, and the resistivity of the crystal is low. As a result, as-grown CZT crystals are often difficult to meet for preparing nuclear radiation detectors, requiring post-processing.
The current treatment methods have a number of drawbacks. For example, CN104532172a discloses a heat treatment method for eliminating defects of tellurium-rich precipitated phases in CZT materials by a two-step method, wherein tellurium sources are used for heat treatment of tellurium-rich CZT first, excess tellurium atoms in the tellurium-rich precipitated phases are removed from crystals, and then cadmium sources are used for heat treatment of the materials, but the method is relatively cumbersome in process and high in cost, and does not involve influence on CZT crystal resistivity. CN102168313a discloses a method for modifying CZT crystals by gas phase annealing, which also adopts a two-step annealing method. The first step adopts nonmetallic tellurium as an annealing source, so that the resistivity and the energy resolution of the crystal are improved; and the second step uses cadmium zinc alloy as annealing source to eliminate inclusion phase in crystal and raise carrier mobility-life product. The tube sealing technology used by the method increases the consumption of the quartz tube, and the annealing time of the method is up to more than 2000 hours, so that the time cost and the economic cost are too high, and the practicability is low.
Therefore, it is a need for a solution to the problem of providing a method for suppressing tellurium-rich inclusion defects and increasing the resistivity of CZT crystals.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention provides a method for inhibiting tellurium-rich inclusion defects in CZT crystals and improving the resistivity of the CZT crystals, which has the characteristics of few operation procedures, short annealing period, high efficiency and low cost, and can improve the resistivity of the CZT crystals while inhibiting the tellurium-rich inclusion defects in the CZT crystals.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a method for inhibiting tellurium-rich inclusion defects in CZT crystals and improving the resistivity of the CZT crystals adopts a method of combining a double-temperature-zone horizontal annealing furnace with open-tube annealing heat treatment, and takes indium and tellurium as annealing sources and nitrogen as protective atmosphere.
Preferably, the specific steps are as follows:
(1) Placing indium, tellurium and CZT crystals in a quartz tube by using a quartz boat, setting a temperature control program through a temperature control operation interface, and then installing a gas cylinder, a gas inlet valve, the quartz tube, a gas outlet valve and a vacuum gas extraction valve;
(2) Closing an air inlet valve, an air outlet valve and a vacuum air exhaust valve of the annealing furnace, opening a mechanical pump, vacuumizing the environment in the quartz tube, unscrewing the vacuum air exhaust valve, closing the vacuum air exhaust valve after the vacuum degree is less than 1Pa, and closing the mechanical pump; opening a gas path according to the sequence of a main valve, a pressure dividing valve and a pipeline switch of the gas cylinder, then opening an air inlet valve, introducing nitrogen into a quartz tube until the pressure in the tube is equal to or slightly greater than the atmospheric pressure, closing an air inlet valve, and stopping introducing the nitrogen;
(3) Repeating the step (2) for 2-5 times, then opening an air inlet valve and an air outlet valve to enable the quartz tube to be filled with nitrogen, and opening a temperature control system operation switch to anneal;
(4) Grinding, mechanical polishing, chemical polishing, ultrasonic cleaning and drying the annealed CZT crystal in a vacuum environment.
Preferably, the double-temperature-zone horizontal annealing furnace consists of a temperature control system, a vacuum system, a gas flow control system and a quartz tube furnace tube.
Preferably, the purity of the quartz tube and the quartz boat is 4-5N.
Preferably, the purity of the quartz tube and the quartz boat is 5N.
Preferably, the purity of the indium and tellurium is 6-7N.
Preferably, the indium and tellurium are particles with the particle size less than or equal to 5 meshes.
Preferably, the purity of indium and tellurium are both 7N.
Preferably, the nitrogen gas is 5N in purity.
Preferably, the CZT crystals have a thickness of 1.0 to 5.0mm.
Preferably, the nitrogen flow rate is 10-100 sccm.
Preferably, the temperature control program comprises a heating rate, a cooling rate, a heat preservation temperature and a heat preservation duration; the heating rate and the cooling rate are 1-10 ℃/min; the heat preservation temperature of the low temperature area is 600-800 ℃, and the heat preservation temperature of the high temperature area is 600-800 ℃; the heat preservation time is 40-120 h.
Preferably, the heating rate and the cooling rate are 5-6 ℃/min; the heat preservation time is 60-70 h.
Preferably, the quartz boat is placed in the following order: the quartz boat for containing indium, tellurium and CZT crystals is sequentially arranged from one side close to the air inlet to one side close to the air outlet of the annealing furnace, wherein the quartz boat for containing indium and tellurium is positioned in a low temperature area, the quartz boat for containing CZT crystals is positioned in a high temperature area, and the distance between the adjacent quartz boats is 5-15 cm.
Preferably, the distance between adjacent quartz boats is 10-15 cm.
Preferably, through hole heat insulation plugs are used for separating the air outlet from the low temperature area and separating the high temperature area from the air inlet.
Preferably, the through hole heat insulation plug is a ceramic alumina heat insulation plug or a quartz heat insulation plug.
Preferably, the through hole heat insulation plug is a quartz heat insulation plug.
The mechanism of the invention is as follows:
the thermomigration mechanism, that is, when the annealing temperature is higher than the melting point of tellurium-rich inclusions in CZT, the tellurium-rich inclusions in a molten state migrate from the inside of the crystal to the surface of the crystal under the action of a temperature gradient, and are removed by polishing the annealed crystal.
The invention uses indium and tellurium atoms to compensate cadmium vacancy in CZT crystal by annealing in indium and tellurium atmosphere. Since the diffusion rate of indium atoms In CZT crystals is greater than that of tellurium atoms, a large number of cadmium vacancies are filled with indium atoms to form shallow donor levels In Cd ] + A small part of cadmium vacancies are compensated by tellurium atoms, resulting in deep donor levels [ Te ] Cd ] 2+ The synergic action of indium and tellurium atoms greatly improves the resistivity of annealed crystals.
Compared with the prior art, the invention has the following beneficial effects:
the annealing method combining the horizontal annealing furnace with the double-temperature-zone independent control and the open tube annealing is adopted, the annealing method does not need tube welding treatment, the operation procedures are few, and the quartz tube can be reused; in addition, the annealing temperature is higher than the melting point of the tellurium-rich inclusion (the melting point of the tellurium-rich inclusion is lower than 500 ℃), and indium and tellurium are used as annealing sources, so that the defect of the tellurium-rich inclusion in the crystal can be restrained, the resistivity of the crystal can be improved, the complex annealing process of a two-step method is avoided, the annealing period is short, the efficiency is higher, and the cost is lower, and the annealing method is a practical annealing method.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic representation of the process of the present invention.
FIGS. 2 (a) and (b) are infrared transmission microscopy images of tellurium-rich inclusions of the CZT crystal of example 1 before and after annealing, respectively.
FIGS. 3 (a) and (b) are infrared transmission microscopy images of tellurium-rich inclusions of the CZT crystal of example 2 before and after annealing, respectively.
FIG. 4 is an I-V curve of the CZT crystal of example 1 before annealing and after annealing for 60 hours in an indium and tellurium atmosphere.
FIG. 5 is an I-V curve of example 2 before annealing and after annealing in an indium and tellurium atmosphere for 70 hours.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
Pretreatment:
(1) Placing a quartz tube and a quartz boat in aqua regia to soak for 4 hours, removing impurities attached to the quartz tube and the quartz boat, then flushing the aqua regia remained on the quartz tube and the quartz boat by using ultrapure water, and finally introducing nitrogen gas into an annealing furnace to bake for 4 hours at the temperature of 800 ℃ to remove water and impurities for later use;
(2) CZT crystals with the thickness of 2.2mm are cut from a CZT ingot, then ground, mechanically polished, chemically polished for 1min by using a bromomethanol solution with the concentration of 5%, sequentially cleaned by using methanol, acetone and ethanol, cleaned by using ultrapure water, and finally dried in a vacuum drying oven with the temperature of 100 ℃ for standby.
A method for inhibiting tellurium-rich inclusion defects in CZT crystals and improving the resistivity of the CZT crystals comprises the following specific steps:
(1) Using a quartz tube, a quartz boat and CZT crystals which are obtained through pretreatment, respectively using the quartz boat to contain indium, tellurium and CZT crystals, placing the crystals in the quartz tube, setting a temperature control program through a temperature control operation interface, and then installing a gas cylinder, a gas inlet valve, the quartz tube, a gas outlet valve and a vacuum pumping valve;
(2) Closing an air inlet valve, an air outlet valve and a vacuum air exhaust valve of the annealing furnace, opening a mechanical pump, vacuumizing the environment in the quartz tube, unscrewing the vacuum air exhaust valve, closing the vacuum air exhaust valve after the vacuum degree is less than 1Pa, and closing the mechanical pump; opening a gas path according to the sequence of a main valve, a pressure dividing valve and a pipeline switch of the gas cylinder, then opening an air inlet valve, introducing nitrogen into a quartz tube until the pressure in the tube is equal to or slightly greater than the atmospheric pressure, closing an air inlet valve, and stopping introducing the nitrogen;
(3) Repeating the step (2) for 3 times, then opening an air inlet valve and an air outlet valve to enable the quartz tube to be filled with nitrogen, and opening a temperature control system operation switch to anneal;
(4) Grinding, mechanically polishing, chemically polishing, ultrasonically cleaning and drying the annealed CZT crystal in a vacuum environment;
the double-temperature-zone horizontal annealing furnace consists of a temperature control system, a vacuum system, a gas flow control system and a quartz tube furnace tube;
the purities of the quartz tube and the quartz boat are 5N;
the purity of the indium and the tellurium is 7N;
the indium and tellurium are particles with the particle size less than or equal to 5 meshes;
the purity of the nitrogen is 5N;
the thickness of the CZT crystal is 2.2mm;
the flow rate of the nitrogen is 40sccm;
the temperature control program comprises a heating rate, a cooling rate, a heat preservation temperature and a heat preservation duration;
according to the principle of a thermal migration mechanism, only if the annealing temperature is higher than the melting point of the tellurium-rich inclusions so as to melt the tellurium-rich inclusions, the tellurium-rich inclusions can migrate from the inside of the crystal to the surface of the crystal. The annealing temperature is generally higher than 500 ℃. Meanwhile, as can be seen from the fine structure phase diagram of the cadmium telluride uniform region at high temperature, the cadmium telluride can undergo solid phase transformation at about 927 ℃, namely, beta phase is converted into alpha phase of sphalerite, and the longer the two-phase coexistence time is, the larger the residual stress in the crystal is, and the poorer the structural integrity of the crystal is. Based on this, setting is made: the heating rate and the cooling rate are 5 ℃/min; the heat preservation temperature of the low temperature area is 600 ℃, and the heat preservation temperature of the high temperature area is 700 ℃; the heat preservation time is 60 hours;
the quartz boat is placed in the following sequence: the quartz boat containing indium, tellurium and CZT crystals is arranged on one side, close to the air inlet of the annealing furnace, to one side, close to the air outlet of the annealing furnace, wherein the quartz boat containing indium and tellurium are both positioned in a low temperature area, the quartz boat containing CZT crystals is positioned in a high temperature area, and the distance between the adjacent quartz boats is 15cm;
the air outlet and the low temperature area are separated by a through hole heat insulation plug;
the through hole heat insulation plug is a ceramic alumina heat insulation plug.
The tellurium-rich inclusion density in the resulting crystal was observed and tested for I-V curves for the crystal as shown in FIGS. 2 and 4, respectively, from 10 before annealing 4 /cm 2 Down to 10 3 /cm 2 The resistivity is 1.767 ×10 before annealing 7 Omega cm to 2.546 ×10 after annealing 10 Ω·cm。
Example 2
Pretreatment:
(1) Placing a quartz tube and a quartz boat in aqua regia to soak for 5 hours, removing impurities attached to the quartz tube and the quartz boat, then using ultrapure water to rinse out the aqua regia remained on the quartz tube and the quartz boat, and finally introducing nitrogen gas into an annealing furnace to bake for 4 hours at 800 ℃ to remove water and impurities for later use;
(2) Cutting CZT crystals with the thickness of 2.5mm from a CZT ingot, grinding, mechanically polishing, chemically polishing for 90s by using a bromomethanol solution with the concentration of 5%, sequentially cleaning the chemically polished crystals by using methanol, acetone and ethanol, cleaning by using ultrapure water, and finally drying in a vacuum drying oven with the temperature of 100 ℃ for later use;
a method for inhibiting tellurium-rich inclusion defects in CZT crystals and improving the resistivity of the CZT crystals comprises the following specific steps:
(1) Using a quartz tube, a quartz boat and CZT crystals which are obtained through pretreatment, respectively using the quartz boat to contain indium, tellurium and CZT crystals, placing the crystals in the quartz tube, setting a temperature control program through a temperature control operation interface, and then installing a gas cylinder, a gas inlet valve, the quartz tube, a gas outlet valve and a vacuum pumping valve;
(2) Closing an air inlet valve, an air outlet valve and a vacuum air exhaust valve of the annealing furnace, opening a mechanical pump, vacuumizing the environment in the quartz tube, unscrewing the vacuum air exhaust valve, closing the vacuum air exhaust valve after the vacuum degree is less than 1Pa, and closing the mechanical pump; opening a gas path according to the sequence of a main valve, a pressure dividing valve and a pipeline switch of the gas cylinder, then opening an air inlet valve, introducing nitrogen into a quartz tube until the pressure in the tube is equal to or slightly greater than the atmospheric pressure, closing an air inlet valve, and stopping introducing the nitrogen;
(3) Repeating the step (2) for 3 times, then opening an air inlet valve and an air outlet valve to enable the quartz tube to be filled with nitrogen, and opening a temperature control system operation switch to anneal;
(4) Grinding, mechanically polishing, chemically polishing, ultrasonically cleaning and drying the annealed CZT crystal in a vacuum environment;
the double-temperature-zone horizontal annealing furnace consists of a temperature control system, a vacuum system, a gas flow control system and a quartz tube furnace tube;
the purity of the quartz tube and quartz boat was the same as in example 1;
the purity of the indium and the tellurium is 7N;
the indium and tellurium are particles with the particle size less than or equal to 5 meshes;
the purity of the nitrogen is 5N;
the thickness of the CZT crystal is 2.5mm;
the flow rate of the nitrogen is 40sccm;
the temperature control program comprises a heating rate, a cooling rate, a heat preservation temperature and a heat preservation duration;
the heating rate and the cooling rate are 5 ℃/min; the heat preservation temperature of the low temperature area is 600 ℃, and the heat preservation temperature of the high temperature area is 700 ℃; the heat preservation time is 70h;
the quartz boat is placed in the following sequence: the quartz boat containing indium, tellurium and CZT crystals is arranged on one side, close to the air inlet of the annealing furnace, to one side, close to the air outlet of the annealing furnace, wherein the quartz boat containing indium and tellurium are both positioned in a low temperature area, the quartz boat containing CZT crystals is positioned in a high temperature area, and the distance between the adjacent quartz boats is 10cm;
the air outlet and the low temperature area are separated by a through hole heat insulation plug;
the through hole heat insulation plug is a quartz heat insulation plug.
The tellurium-rich inclusion density in the resulting crystal was observed and tested for I-V curves for the crystal as shown in FIGS. 3 and 5, respectively, from 10 before annealing 4 /cm 2 Down to 10 3 /cm 2 The resistivity is 2.172×10 before annealing 7 Omega cm to 5.685 ×10 after annealing 10 Ω·cm。
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the solution disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant points refer to the description of the method section.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for inhibiting tellurium-rich inclusion defects in CZT crystals and improving the resistivity of the CZT crystals is characterized in that a method of combining a double-temperature-zone horizontal annealing furnace with open-tube annealing heat treatment is adopted, indium and tellurium are used as annealing sources, and nitrogen is used as protective atmosphere.
2. The method for inhibiting tellurium-rich inclusion defects and increasing the resistivity of CZT crystals as recited in claim 1, wherein the steps of:
(1) Placing indium, tellurium and CZT crystals in a quartz tube by using a quartz boat, setting a temperature control program through a temperature control operation interface, and then installing a gas cylinder, a gas inlet valve, the quartz tube, a gas outlet valve and a vacuum gas extraction valve;
(2) Closing an air inlet valve, an air outlet valve and a vacuum air exhaust valve of the annealing furnace, opening a mechanical pump, vacuumizing the environment in the quartz tube, unscrewing the vacuum air exhaust valve, closing the vacuum air exhaust valve after the vacuum degree is less than 1Pa, and closing the mechanical pump; opening a gas path according to the sequence of a main valve, a pressure dividing valve and a pipeline switch of the gas cylinder, then opening an air inlet valve, introducing nitrogen into a quartz tube until the pressure in the tube is equal to or slightly greater than the atmospheric pressure, closing an air inlet valve, and stopping introducing the nitrogen;
(3) Repeating the step (2) for 2-5 times, then opening an air inlet valve and an air outlet valve to enable the quartz tube to be filled with nitrogen, and opening a temperature control system operation switch to anneal;
(4) Grinding, mechanical polishing, chemical polishing, ultrasonic cleaning and drying the annealed CZT crystal in a vacuum environment.
3. The method for suppressing defects and increasing resistivity of tellurium-rich inclusions within CZT crystals as recited in claim 2, wherein the quartz tube and the quartz boat are each of 4 to 5N purity.
4. The method for inhibiting defects and increasing resistivity of tellurium-rich inclusions within CZT crystals of claim 2, wherein the purity of both indium and tellurium is from 6 to 7N; the indium and tellurium are particles with the particle size less than or equal to 5 meshes.
5. The method of suppressing and increasing resistivity of internal tellurium-rich inclusions of CZT crystals of claim 2, wherein the nitrogen gas is 5N pure.
6. The method of suppressing and increasing the resistivity of tellurium-rich inclusions within CZT crystals as recited in claim 2, wherein the CZT crystals have a thickness of 1.0 to 5.0mm.
7. The method for suppressing defects and increasing resistivity of tellurium-rich inclusions within CZT crystals as recited in claim 2, wherein the nitrogen flow is 10-100 sccm.
8. The method for inhibiting tellurium-rich inclusion defects and increasing the resistivity of CZT crystals according to claim 2, wherein the temperature control program comprises a heating rate, a cooling rate, a holding temperature, a holding time; the heating rate and the cooling rate are 1-10 ℃/min; the heat preservation temperature of the low temperature area is 600-800 ℃, the heat preservation temperature of the high temperature area is 600-800 ℃, and the heat preservation temperature of the low temperature area is lower than that of the high temperature area; the heat preservation time is 40-120 h.
9. The method for suppressing defects and increasing resistivity of tellurium-rich inclusions within CZT crystals as recited in claim 2, wherein the quartz boat is placed in the order of: the quartz boat for containing indium, tellurium and CZT crystals is sequentially arranged from one side close to the air inlet to one side close to the air outlet of the annealing furnace, wherein the quartz boat for containing indium and tellurium is positioned in a low temperature area, the quartz boat for containing CZT crystals is positioned in a high temperature area, and the distance between the adjacent quartz boats is 5-15 cm.
10. The method of suppressing and increasing the resistivity of tellurium-rich inclusions within CZT crystals of claim 9, wherein a through-hole insulating plug is used between the gas outlet and the low temperature zone and between the high temperature zone and the gas inlet.
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