Ionic Semiconductor Radiation Detector Liquid Contact Stability
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Solution Overview
Problem
Ionic semiconductor detectors, such as thallium bromide, face performance issues like reduced internal field and detector instability due to polarization under applied bias at room temperature, limiting their widespread use in radiation detection applications.
Innovation Solution
The use of ionic semiconductor materials with electrical contacts comprising a liquid with ions capable of associating with ionic species from the semiconductor material, or metal layers like Cr, Ti, W, and Pb, which form a substantial interface and have a thickness greater than or equal to 40 nm, to enhance stability and prevent accumulation of ionic species.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ionic semiconductor detectors are operated at room temperature under applied bias, then they can detect radiation with high photoelectric and total attenuation coefficients, but polarization occurs causing reduced internal field and detector instability
Solution Approach 1:
A liquid contact comprising ions is introduced as an intermediary between the ionic semiconductor material and the external electrical contact. This liquid contact acts as a mediator that accepts ionic species from the semiconductor material, preventing their accumulation at the semiconductor-electrical contact interface. The ions in the liquid contact (such as NH4+, K+, Na+, Cs+, or Ca2+) associate with the ionic species (Br-, I-, Cl-, or F-) from the semiconductor, thereby eliminating the harmful polarization effect while maintaining stable electrical contact.
Solution Approach 2:
The invention changes the physical state of the electrical contact from solid to liquid, and modifies the chemical composition by introducing mobile ions into the contact. This parameter change allows the contact to dynamically adjust and accept ionic species, transforming the static polarization problem into a dynamic solution where ions can move and associate within the liquid phase, preventing charge accumulation and maintaining field stability.
2Reliability
If electrical contacts are made with solid materials, then electrical connection is established, but ionic species accumulate at the interface causing polarization and performance degradation
Solution Approach 1:
The liquid contact serves as an intermediary layer between the solid semiconductor and the external circuit. It provides a mobile ionic environment that can accommodate and associate with ionic species from the semiconductor, preventing their accumulation at the interface. This intermediary liquid phase maintains stable charge collection by allowing continuous ion association without forming stable polarized layers that would degrade performance.
3Reliability
If metal layers are used to form the electrical contact interface, then contact stability is improved, but the interface must be sufficiently thick (≥40 nm) to prevent ionic species accumulation
Solution Approach 1:
The invention uses a liquid (hydraulic) contact instead of a solid metal layer. The liquid contact comprises ions that can mobilely associate with ionic species from the semiconductor, providing stability through fluid dynamics and ionic association rather than through the thickness and structural complexity of solid metal layers. This eliminates the need for multi-layer metal structures with specific thickness requirements.
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 described configuration improves the stability and charge collection efficiency of radiation detectors, allowing them to operate reliably for extended periods at room temperature under continuous bias without significant polarization or damage to the electrical contacts.
Implementation Method 1
the liquid comprises ions capable of associating with an ionic species originating from the ionic semiconductor material
Implementation Method 2
Semiconductor detectors, such as silicon avalanche photodiodes (Si-APDs), are widely used for the detection of X-rays, gamma-rays
Data Source
AI summary
A detector for detecting radiation is generally described. The detector can comprise at least one ionic semiconductor material. For example, the ionic semiconductor material comprises a thallium halide and/or an indium halide. Electrical contacts are formed on the semiconductor material to provide a voltage to the detector during use. At least one of the electrical contacts may comprise a liquid that contains ions. In some instances, at least one electrical contact comprises a metal, such as Cr, Ti, W, Mo, or Pb. In some embodiments, the detector comprises both an electrical contact comprising liquid comprising ions and an electrical contact comprising a metal selected from a group consisting of Cr, Ti, W, Mo, and Pb. Detectors for detecting radiation, as described herein, may have beneficial properties.