Based on LiGa 0.5 In 0.5 Self-driven X-ray detector based on Se2 crystal and its fabrication method

Abstract

A LiGa-based 0.5 In 0.5 A self-driven X-ray detector based on Se2 crystal and its fabrication method. This detector employs an MSM device structure with c-plane LiGa... 0.5 In 0.5 Using Se2 wafers as semiconductor materials and metal materials as electrodes, self-driven X-ray detection can be achieved under zero bias voltage; the above-mentioned self-driven X-ray detector fabrication method includes the following steps: (1) fabricating LiGa 0.5 In 0.5 (1) Se2 crystal; (2) Directional processing of c-plane LiGa 0.5 In 0.5 Se2 wafer; (3) LiGa 0.5 In 0.5 The upper and lower surfaces of the Se2 wafer are polished and passivated; (4) in LiGa 0.5 In 0.5 Metal electrodes are deposited on the upper and lower surfaces of a Se2 wafer. This invention utilizes LiGa... 0.5 In 0.5 The bulk photovoltaic effect generated by the non-centrosymmetric structure of Se2 enabled the fabrication of a self-driven X-ray detector with a simple structure. Furthermore, due to the LiGa... 0.5 In 0.5 Se2 crystals have high resistivity, and the devices fabricated from them have low dark current, enabling highly sensitive X-ray detection.

Description

Technical Field

[0001] This invention relates to a LiGa-based 0.5 In 0.5 The self-driven X-ray detector of Se2 crystal and its preparation method belong to the field of X-ray detection technology. Technical Background

[0002] X-ray detectors are widely used in non-destructive testing, security inspection, and medical diagnostics. Their principle is that X-rays interact with the detection material to generate charge carriers, which then move directionally within the material, producing an electrical signal response. Self-driven X-ray detection refers to the ability to collect and detect electrical signals without an external bias voltage, making it valuable for low-power, high-sensitivity X-ray detection.

[0003] The basic principles of self-driven X-ray detection include bulk photovoltaic effect, heterojunction, and PN junction. Heterojunction and PN junction detectors have complex fabrication processes, while bulk photovoltaic-based X-ray detection utilizes the bulk photovoltaic effect of non-centrosymmetric materials under X-ray irradiation to generate photogenerated electrons and holes, which are then effectively separated at zero bias voltage for detection. Compared to traditional PN junction self-driven X-ray detectors, bulk photovoltaic-based self-driven X-ray detectors require only a single polarity material for X-ray detection, avoiding complex material interface engineering. They offer advantages such as simple device fabrication, high photovoltage, fast response speed, and high tolerance to material defects, making them highly promising for applications in the field of self-driven X-ray detection.

[0004] Currently, X-ray detectors based on perovskite materials have attracted widespread attention, but they suffer from problems such as Pb toxicity, poor material stability, and weak bulk photovoltaic effect, which limit their application in the field of self-driven X-ray detection.

[0005] Lithium indium selenide (LiGa) 0.5 In 0.5 Se2) crystal is a polar crystal with a non-centrosymmetric structure, belonging to the orthorhombic crystal system and space group Pna21. This crystal has a suitable band gap (2.22 eV) and high resistivity (2.36 × 10⁻⁶). 12 The intrinsic polar structure (Ωcm) leads to a strong bulk photovoltaic effect and excellent properties such as good stability. Furthermore, the material itself does not contain Pb, making it non-toxic and environmentally friendly. Therefore, based on LiGa... 0.5 In 0.5 Se2 crystals can achieve highly sensitive, low-detection-limit self-driven X-ray detection, and have great application prospects in the field of low-power X-ray detection.

[0006] However, there are currently no LiGa-based [products / technology] 0.5 In 0.5Specific applications of Se2 crystals in self-driven X-ray detection. Summary of the Invention

[0007] This invention addresses the shortcomings of current self-driven X-ray detection technologies, such as low sensitivity and poor material stability, by designing a LiGa-based X-ray detection system with a simple structure that achieves high sensitivity and low detection limit. 0.5 In 0.5 Self-driven X-ray detector using Se2 crystal.

[0008] This invention is based on LiGa 0.5 In 0.5 The self-driven X-ray detector using Se2 crystals employs the following technical solution:

[0009] This self-driven X-ray detector has an MSM device structure with c-plane LiGa 0.5 In 0.5 Using Se2 wafers as semiconductor materials and metallic materials as electrodes, self-driven X-ray detection can be achieved under zero bias voltage.

[0010] The direction of the current generated by the electrode is parallel to the c-axis of the crystal.

[0011] The wafer size is 6×6mm. 2 -8×8mm 2 .

[0012] The thickness of the wafer is 1.5mm-2mm.

[0013] The metallic material is gold or silver.

[0014] The electrode thickness is 60nm-100mm.

[0015] Due to LiGa 0.5 In 0.5 Se2 crystal is a polar crystal with a non-centrosymmetric structure and a large dipole moment in the c-direction, which can generate a strong bulk photovoltaic effect, thus facilitating self-driven X-ray detection. Meanwhile, LiGa... 0.5 In 0.5 Se2 crystal has a suitable band gap (2.22 eV) and high resistivity (2.36 × 10⁻⁶ eV). 12 (Ωcm) and good stability. Therefore, based on LiGa 0.5 In 0.5 The self-driven X-ray detector based on Se2 crystal has high sensitivity and low detection limit, enabling high-performance self-driven X-ray detection.

[0016] This invention is based on LiGa 0.5 In 0.5The method for fabricating a self-driven X-ray detector using Se2 crystals includes the following steps:

[0017] (1) Preparation of LiGa 0.5 In 0.5 Se2 crystals;

[0018] (2) Directional machining of c-plane LiGa 0.5 In 0.5 Se2 chips;

[0019] LiGa 0.5 In 0.5 The Se2 chip size is 6×6mm. 2 -10×10mm 2 The thickness is 1.5mm-2mm.

[0020] (3) LiGa 0.5 In 0.5 The upper and lower surfaces of the Se2 wafer are polished and then passivated.

[0021] The surface passivation process involves applying LiGa... 0.5 In 0.5 Se2 wafers were immersed in a 30% H2O2 solution at 80-85℃ for 1-1.5 hours.

[0022] (4) In LiGa 0.5 In 0.5 Metal electrodes are vapor-deposited on the upper and lower surfaces of the Se2 wafer.

[0023] In step (1), LiGa is prepared 0.5 In 0.5 The process of Se2 crystal formation is as follows:

[0024] ① The raw materials were mixed in a molar ratio of Li:Ga:In:Se = 2:1:1:4. The elemental raw materials were then placed in a pretreated graphite crucible and mixed evenly. The mixture was then placed in a pretreated quartz ampoule, and after vacuuming, the ampoule was sintered and sealed.

[0025] ②The quartz ampoule is heated in stages to allow the raw materials to fully react;

[0026] The phased heating process involves first raising the temperature to 200-250℃ over 30-40 hours and holding it at that temperature for 25-35 hours; then raising the temperature to 600-650℃ over 30-40 hours and holding it at that temperature for 30-40 hours; and finally raising the temperature to 900-950℃ and holding it at that temperature for 40-50 hours.

[0027] ③ After the reaction is complete, allow it to cool to room temperature;

[0028] The time required to cool to room temperature is 50 to 60 hours.

[0029] ④ Break the quartz ampoule and remove the LiGa from the crucible. 0.5 In 0.5 Se2 polycrystalline material, ground into LiGa 0.5 In 0.5 Se2 powder;

[0030] ⑤ Grind LiGa 0.5 In 0.5 Se2 powder was loaded into a pretreated graphite crucible, then placed in a pretreated quartz ampoule, and sealed by vacuum sintering.

[0031] ⑥ Melt the quartz ampoule at 850–900℃ for 30–40 hours, then lower it to the 800–850℃ position at a rate of 0.15–0.3 mm / h, and then cool it to room temperature at a rate of 1–2℃ / h. Break the quartz ampoule and remove the LiGa from the crucible. 0.5 In 0.5 Se2 crystal.

[0032] The pretreated graphite crucibles in ① and ⑤ are prepared by polishing the inner wall, cleaning and drying.

[0033] The pretreated quartz ampoules mentioned in ① and ⑤ are prepared by immersing the quartz ampoules in a dilute hydrochloric acid solution (mass fraction of 10%) for 20 hours, followed by cleaning with deionized water and anhydrous ethanol in sequence.

[0034] The vacuum level evacuated in ① and ⑤ is ≤10. -4 Pa;

[0035] In step ⑥, the quartz ampoule is placed in the high-temperature zone of the Bridgman furnace, and the temperatures of the high-temperature zone and the low-temperature zone of the Bridgman furnace are set to 850–900°C and 650–700°C, respectively.

[0036] Due to LiGa 0.5 In 0.5 Se2 crystals possess a polar structure with a large dipole moment along the c-axis. Based on c-axis LiGa... 0.5 In 0.5 The detector fabricated on the Se2 wafer generates charge carriers when irradiated with X-rays. The photogenerated charge carriers move along the c-axis of the crystal to the two ends of the electrode, thereby generating a photocurrent without bias voltage, thus realizing self-driven X-ray detection.

[0037] The self-driven X-ray detector prepared above was tested using a semiconductor testing system with X-rays of 40 keV photon energy and a dose rate of 2.944–7.429 μGy / s. Under no bias voltage, the device achieved a sensitivity as high as 354 μC Gy. -1 cm -2This is far higher than the sensitivity of commercial X-ray detectors based on α-Se (20 μC Gy). -1 cm -2 The detector's detection limit is as low as 125.5 nGy / s. The performance of self-driven X-ray detectors based on other materials is shown in Table 1. Compared to detectors made from other materials, LiGa... 0.5 In 0.5 Se2 crystal X-ray detectors have outstanding performance advantages such as high sensitivity and low detection limit, as detailed in Table 1.

[0038] Table 1 Comparison of self-driven X-ray detection performance of different materials

[0039]

[0040] This invention utilizes LiGa 0.5 In 0.5 The bulk photovoltaic effect generated by the non-centrosymmetric polar structure of Se2 crystal was used to design and fabricate a self-driven X-ray detector. The device has a simple structure and high process stability. Additionally, LiGa... 0.5 In 0.5 Se2 crystals have high resistivity, which is beneficial for reducing dark current; therefore, LiGa... 0.5 In 0.5 Se2 crystal X-ray detectors can achieve highly sensitive X-ray detection. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of the self-driven detector of the present invention.

[0042] Figure 2 It is the LiGa in Example 1 0.5 In 0.5 Photo of Se2 chip.

[0043] Figure 3 The LiGa used in Example 1 0.5 In 0.5 High-resolution X-ray single-crystal rocking curve of Se2 crystal.

[0044] Figure 4 This is the IV curve of the self-driven X-ray detector prepared in Example 1.

[0045] Figure 5 This is the It curve of the self-driven X-ray detector prepared in Example 1 under no bias voltage.

[0046] Figure 6 This is the detection limit curve of the self-driven X-ray detector prepared in Example 1.

[0047] Among them: 1. Metal electrode, 2. LiGa0.5 In 0.5 Se2 wafer, 3. X-rays with photon energy of 40keV. Detailed Implementation

[0048] This invention aims to provide a highly sensitive self-driven X-ray detector based on a polar crystal, which is made of LiGa 0.5 In 0.5 The device is constructed from Se2 crystals and designed as a metal-semiconductor-metal (MSM) structure. Based on the bulk photovoltaic effect generated by the intrinsic polar structure of the crystal, it achieves highly sensitive X-ray detection. The structure of the device is as follows: Figure 1 As shown, LiGa 0.5 In 0.5 Se2 crystals are used as semiconductor materials in LiGa 0.5 In 0.5 Metal electrodes 1 are deposited on the upper and lower surfaces of the Se2 wafer 2, and the device structure is a simple metal-semiconductor-metal (MSM) structure. This device can detect X-rays 3 with photon energies of 40 keV at zero bias.

[0049] Figure 2 The present invention provides the LiGa4 used in the fabrication of a self-driven X-ray detector. 0.5 In 0.5 Optical photograph of Se2 crystal. Figure 3 The high-resolution X-ray single-crystal rocking curve of this crystal is presented.

[0050] The following describes in detail the specific fabrication process of the self-driven X-ray detector based on the bulk photovoltaic effect of the present invention with reference to the accompanying drawings and embodiments.

[0051] The instruments used in each embodiment are: (1) graphite crucible; (2) single-temperature zone well furnace; (3) graphite crucible; (4) quartz ampoule; (5) Bridgman furnace, whose two temperature zones are independently controlled by a programmable temperature controller, with the high temperature zone and low temperature zone set to 850-900℃ and 650-700℃ respectively; (6) glove box; (7) vacuum evaporation machine.

[0052] The graphite crucible undergoes the following pretreatment: the inner wall is polished smooth, cleaned, and dried.

[0053] The quartz ampoules were pretreated by immersing them in a dilute hydrochloric acid solution (10% by mass) for 20 hours, followed by cleaning them with deionized water and anhydrous ethanol.

[0054] Example 1

[0055] This embodiment utilizes 6×6×2mm 3 LiGa 0.5 In0.5 The steps for fabricating a self-driven X-ray detector using Se2 crystals are as follows:

[0056] (1) In a glove box, the raw materials were mixed in a molar ratio of Li:Ga:In:Se = 2:1:1:4. The elemental raw materials were then placed into a pretreated graphite crucible and mixed thoroughly. The mixture was then placed in a pretreated quartz ampoule and evacuated to ≤10°C. -4 After Pa, the tube is sintered and sealed.

[0057] (2) Place the quartz ampoule in a single-temperature zone well furnace and adopt a staged heating program. First, heat up to 200°C in 30 hours and keep it at a constant temperature for 35 hours; then, heat up to 600°C in 30 hours and keep it at a constant temperature for 30 hours; finally, heat up to 900°C and keep it at a constant temperature for 40 hours.

[0058] (3) After the reaction is complete, cool the furnace body to room temperature for 60 hours and remove the quartz ampoule;

[0059] (4) Crush the ampoule and remove the LiGa from the graphite crucible. 0.5 In 0.5 Se2 polycrystalline material, ground into LiGa 0.5 In 0.5 Se2 powder.

[0060] (5) Grind LiGa 0.5 In 0.5 Se2 powder was loaded into a graphite crucible, then placed in a pretreated quartz ampoule, and evacuated to ≤10 °C. -4 After Pa, it is sintered and sealed.

[0061] (6) Place the quartz ampoule in the high-temperature zone of the Bridgman furnace (the high-temperature zone and the low-temperature zone are set to 850℃ and 700℃ respectively), melt it at 850℃ for 30 hours, then lower it to 800℃ at a rate of 0.15 mm / h, and then cool it to room temperature at a rate of 1℃ / h. Remove the quartz ampoule, break it, and remove the LiGa from the crucible. 0.5 In 0.5 Se2 crystal.

[0062] (7) For LiGa 0.5 In 0.5 The Se2 crystal is oriented to determine the c-plane of the crystal.

[0063] (8) Cut and process the c-axis wafer, with a wafer size of 6×6mm. 2 The thickness is 2mm.

[0064] (9) The cut c-axis wafer is precision polished. The polished crystal is placed in a 30% H2O2 solution. The solution is then heated to 80°C and kept at a constant temperature for 1 hour for surface passivation treatment. After passivation, the crystal is cleaned with deionized water and anhydrous ethanol in sequence and then dried.

[0065] (10) The passivated crystal was used to prepare a metal electrode by thermal evaporation technology, gold was selected as the electrode material and the electrode thickness was 60 nm.

[0066] Figure 4 The IV curves of the self-driven X-ray detector device prepared in this embodiment are presented, showing large open-circuit voltage and short-circuit current. The voltage and current show a good linear relationship, proving that there is good ohmic contact between the electrode and the material.

[0067] Figure 5 The It curve of the self-driven X-ray detector prepared in this embodiment under no bias voltage is given. It shows that at 0V, it exhibits good response at different dose rates of 40keV, with a sensitivity as high as 354μC Gy. -1 cm -2 This demonstrates its self-driven X-ray detection capability.

[0068] Figure 6 The detection limit measurement results of the self-driven X-ray detector device prepared in this embodiment are given. The detection limit of the device is as low as 125.5 nGy / s under no bias voltage.

[0069] Example 2

[0070] This embodiment utilizes 8×8×1.5mm 3 LiGa 0.5 In 0.5 The steps for fabricating a self-driven X-ray detector using Se2 crystals are as follows:

[0071] (1) In a glove box, the raw materials were mixed in a molar ratio of Li:Ga:In:Se = 2:1:1:4. The elemental raw materials were then placed into a pretreated graphite crucible and mixed thoroughly. The mixture was then placed in a pretreated quartz ampoule and evacuated to ≤10°C. -4 After Pa, the tube is sintered and sealed.

[0072] (2) Place the quartz ampoule in a single-temperature zone well furnace and adopt a staged heating program. First, heat up to 220°C in 35 hours and keep it at that temperature for 25 hours; then, heat up to 630°C in 35 hours and keep it at that temperature for 40 hours; finally, heat up to 920°C and keep it at that temperature for 42 hours.

[0073] (3) After the reaction is complete, cool the furnace body to room temperature for 50 hours and remove the quartz ampoule;

[0074] (4) Crush the ampoule and remove the LiGa from the graphite crucible. 0.5 In 0.5 Se2 polycrystalline material, ground into LiGa 0.5 In 0.5 Se2 powder.

[0075] (5) Grind LiGa 0.5 In 0.5 Se2 powder was loaded into a graphite crucible, then placed in a pretreated quartz ampoule, and evacuated to ≤10 °C. -4 After Pa, it is sintered and sealed.

[0076] (6) Place the quartz ampoule in the high-temperature zone of a Bridgeman furnace (the high-temperature zone and the low-temperature zone are set to 900℃ and 700℃ respectively), melt it at 880℃ for 35 hours, then lower it to 830℃ at a rate of 0.3 mm / h, and then cool it to room temperature at a rate of 2℃ / h. Remove the quartz ampoule, break it, and remove the LiGa from the crucible. 0.5 In 0.5 Se2 crystal.

[0077] (7) For LiGa 0.5 In 0.5 The Se2 crystal is oriented to determine the c-plane of the crystal.

[0078] (8) Cut and process the c-axis wafer, with a wafer size of 8×8mm. 2 The thickness is 1.5mm.

[0079] (9) The cut c-axis wafer is precision polished. The polished crystal is placed in a 30% H2O2 solution and then heated to 85°C and kept at a constant temperature for 1.5 hours for surface passivation treatment. The passivated crystal is then cleaned with deionized water and anhydrous ethanol in sequence and then dried.

[0080] (10) The passivated crystal was used to prepare a metal electrode by thermal evaporation technology, with silver as the electrode material and an electrode thickness of 80 nm.

[0081] Example 3

[0082] This embodiment utilizes 10×10×2mm 3 LiGa 0.5 In 0.5 The steps for fabricating a self-driven X-ray detector using Se2 crystals are as follows:

[0083] (1) In a glove box, the raw materials were mixed in a molar ratio of Li:Ga:In:Se = 2:1:1:4. The elemental raw materials were then placed into a pretreated graphite crucible and mixed thoroughly. The mixture was then placed in a pretreated quartz ampoule and evacuated to ≤10°C. -4After Pa, the tube is sintered and sealed.

[0084] (2) Place the quartz ampoule in a single-temperature zone pit furnace and adopt a staged heating program. First, heat up to 250°C in 40 hours and keep it at that temperature for 20 hours; then, heat up to 650°C in 40 hours and keep it at that temperature for 35 hours; finally, heat up to 950°C and keep it at that temperature for 50 hours.

[0085] (3) After the reaction is complete, cool the furnace body to room temperature for 55 hours and then remove the quartz ampoule;

[0086] (4) Crush the ampoule and remove the LiGa from the graphite crucible. 0.5 In 0.5 Se2 polycrystalline material, ground into LiGa 0.5 In 0.5 Se2 powder.

[0087] (5) Grind LiGa 0.5 In 0.5 Se2 powder was loaded into a graphite crucible, then placed in a pretreated quartz ampoule, and evacuated to ≤10 °C. -4 After Pa, it is sintered and sealed.

[0088] (6) Place the quartz ampoule in the high-temperature zone of a Bridgman furnace (the high-temperature zone and the low-temperature zone are set to 860℃ and 650℃ respectively), melt it at 900℃ for 40 hours, then lower it to 850℃ at a rate of 0.2 mm / h, and then cool it to room temperature at a rate of 1.5℃ / h. Remove the quartz ampoule, break it, and remove the LiGa from the crucible. 0.5 In 0.5 Se2 crystal.

[0089] (7) For LiGa 0.5 In 0.5 The Se2 crystal is oriented to determine the c-plane of the crystal.

[0090] (8) Cut and process the c-axis wafer, with a wafer size of 10×10mm. 2 The thickness is 2mm.

[0091] (9) The cut c-axis wafer is precision polished. The polished crystal is placed in a 30% H2O2 solution and then heated to 82℃ and kept at a constant temperature for 1.2h for surface passivation treatment. The passivated crystal is then cleaned with deionized water and anhydrous ethanol in sequence and then dried.

[0092] (10) The passivated crystal was used to prepare a metal electrode by thermal evaporation technology, gold was selected as the electrode material and the electrode thickness was 100 nm.

Claims

1. A LiGa 0.5 In 0.5 A method for preparing a self-driven X-ray detector of Se2 crystal, which is an MSM device structure, c-plane LiGa 0.5 In 0.5 Se2 wafer as a semiconductor material, metal material as an electrode, and self-driven X-ray detection under zero bias voltage; characterized in that, It comprises the following steps: (1) Preparation of LiGa 0.5 In 0.5 Se2 crystal; (2) Oriented processing of c-plane LiGa 0.5 In 0.5 Se2 wafer; (3) LiGa 0.5 In 0.5 The upper and lower surfaces of the Se2 wafer are polished and surface passivation treatment is performed. (4) In LiGa 0.5 In 0.5 Se2 wafer on the upper and lower surfaces of the metal electrode evaporation; The LiGa prepared in the step (1) 0.5 In 0.5 The process of Se2 crystal is: ①According to the proportion of Li:Ga:In:Se=2:1:1:4, the single element raw materials are mixed and put into the pretreated graphite crucible, and then put into the pretreated quartz ampoule, sintered and sealed after vacuumizing; ②The quartz ampoule is heated in stages to make the raw materials fully react; The heating in stages is first heated to 200-250℃ for 30-40 hours, and then kept constant for 25-35 hours; then heated to 600-650℃ for 30-40 hours, and kept constant for 30-40 hours; finally heated to 900-950℃, and kept constant for 40-50 hours; ③After the reaction is completed, the temperature is decreased to room temperature; (4) Knock quartz ampoule, remove LiGa from crucible 0.5 In 0.5 Se2 polycrystalline material, ground into LiGa 0.5 In 0.5 Se2 powder; (5) The milled LiGa 0.5 In 0.5 The Se2 powder was loaded into a pre-treated graphite crucible, which was then placed in a pre-treated quartz ampoule, which was evacuated and sintered and sealed. (6) The quartz ampoule is melted at 850-900°C for 30-40 hours, then lowered to a position of 800-850°C at a lowering rate of 0.15-0.3 mm / h, then lowered to room temperature at a lowering rate of 1-2°C / h, the quartz ampoule is knocked and LiGa is taken out from the crucible 0.5 In 0.5 Se2 crystal.

2. The LiGa-based battery of claim 1 0.5 In 0.5 A method for manufacturing a self-driven X-ray detector of Se2 crystals, characterized by, The graphite crucible pre-processed in steps 1 and 5 is polished smooth, cleaned and dried; the quartz ampoule pre-processed in steps 1 and 5 is soaked in dilute hydrochloric acid solution for 20 hours, then cleaned with deionized water and anhydrous ethanol; the vacuum degree of the vacuumization in steps 1 and 5 is ≤10 -4 Pa; in step 6, the quartz ampoule is placed in the high-temperature zone of the Bridgman furnace, and the high-temperature zone and the low-temperature zone of the Bridgman furnace are set to 850-900℃ and 650-700℃, respectively.

3. The LiGa-based battery of claim 1 0.5 In 0.5 A method for manufacturing a self-driven X-ray detector of Se2 crystals, characterized by, The time for decreasing to room temperature in the step ③ is 50-60 hours.

4. The LiGa-based battery of claim 1 0.5 In 0.5 A method for manufacturing a self-driven X-ray detector of Se2 crystals, characterized by, The surface passivation treatment process in the step (3) is to immerse the LiGa 0.5 In 0.5 The Se2 wafer is immersed in a 30% H2O2 solution at 80-85°C for 1-1.5 h.

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