Tin Oxide Radiation Detector High Resistivity
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Solution Overview
Problem
Current radiation detecting apparatuses using Si or Ge require thick semiconductor layers, limiting their downsizing and application range due to long X-ray absorption lengths, and materials like CdTe or a-Se have toxicity issues and low sensitivity, while ZnO has low sensitivity and high dark current.
Innovation Solution
A radiation detecting element utilizing a tin oxide crystal (SnO2) with high resistivity (≥107 Ω·cm) is developed, allowing for efficient X-ray absorption and low dark current, achieved through a thermal treatment process enhancing resistivity and minimizing impurity incorporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thick semiconductor layer is used to absorb X-ray completely, then detection sensitivity is improved, but apparatus size increases and downsizing is limited
Solution Approach 1:
The invention changes the material parameter from conventional semiconductors (Si, Ge) to tin oxide crystal with specifically controlled high resistivity (≥10^7 Ω·cm). This parameter change enables the semiconductor layer to achieve both sufficient X-ray absorption and reduced dark current, allowing thinner layer thickness while maintaining detection sensitivity, thus resolving the contradiction between detection sensitivity and apparatus size.
2Volume of moving object
If materials like CdTe, CdZnTe, HgI2, PbI2, or a-Se are used to reduce absorption length, then apparatus downsizing is enabled, but toxicity increases and environmental load worsens
Solution Approach 1:
The invention converts the previously harmful aspect of tin oxide (its tendency to have low resistivity and high dark current, similar to other chalcogenide materials) into a benefit by implementing a specific manufacturing process that achieves ultra-high resistivity (≥10^7 Ω·cm). This transforms tin oxide from an unsuitable material into an ideal choice that combines low toxicity with excellent detection performance, enabling apparatus downsizing without environmental harm.
3Object-affected harmful factors
If ZnO is used as a low-toxicity material, then environmental load is reduced, but sensitivity decreases and dark current increases
Solution Approach 1:
The invention changes the key parameter of resistivity from the typical low values found in conventional semiconductor materials to an ultra-high value of ≥10^7 Ω·cm through controlled crystal growth and thermal treatment processes. This dramatic parameter change in tin oxide crystal simultaneously reduces dark current and enhances X-ray absorption efficiency, achieving high detection sensitivity while maintaining low environmental load, thus resolving the contradiction between environmental friendliness and detection sensitivity.
4Measurement precision
If high voltage (about 10 kV) is applied to collect charges in a-Se, then charge collection efficiency is improved, but power consumption increases and device complexity increases
Solution Approach 1:
The invention changes the electrical parameter of resistivity to ultra-high values (≥10^7 Ω·cm), which fundamentally alters the electrical field distribution and charge carrier behavior in the semiconductor layer. This parameter change enables efficient charge collection at much lower voltages compared to conventional materials like a-Se, thereby reducing power consumption and simplifying the voltage supply requirements while maintaining high charge collection efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The SnO2-based radiation detecting element achieves high sensitivity and low dark current, enabling effective X-ray detection with reduced apparatus size and toxicity, suitable for medical and industrial applications.
Implementation Method 1
charges generated in the semiconductor layer when the semiconductor layer is irradiated with radiation
Implementation Method 2
achieved through a thermal treatment process enhancing resistivity and minimizing impurity incorporation
Data Source
AI summary
Provided is a radiation detecting element, including: a semiconductor layer including a tin oxide crystal; and a detecting unit configured to detect, as an electrical signal, charges generated in the semiconductor layer when the semiconductor layer is irradiated with radiation, in which a resistivity of the semiconductor layer is 107 Ω·cm or more.