UV Detector Rocksalt CaS Diode Solar-Blind Flame Detection
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Solution Overview
Problem
Conventional fire detection methods, such as smoke detectors, suffer from high false alarm rates and slow response times, making them inadequate for reliable fire detection, especially in environments like car parks where exhaust fumes can trigger false alarms, and they are not suitable for solar-blind UV flame detection which requires high sensitivity and speed.
Innovation Solution
A UV radiation detector using a Schottky-barrier diode with a rocksalt phase crystalline structure of CaS or CaTe as the active layer, fabricated through a multi-step molecular beam epitaxy process, which operates in the solar-blind spectrum (220-280 nm) with zero-bias mode and high visible rejection, enabling fast and accurate flame detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If smoke detectors are used for fire detection, then the detection coverage is broad, but the false alarm rate increases and response time slows down
Solution Approach 1:
The patent changes the detection parameter from visible/IR spectrum (smoke detectors) to UV spectrum (220-280 nm, solar-blind region). This parameter change allows the detector to ignore exhaust fumes that trigger smoke detectors while responding to UV radiation from flames, thereby reducing false alarms while maintaining broad detection coverage
Solution Approach 2:
The patent uses a Schottky-barrier diode with rocksalt phase CaS or CaTe active layer that has specific optical properties tailored for UV detection. This localized material selection provides high UV sensitivity while inherently rejecting visible light, achieving both broad UV coverage and high reliability through material-specific optical characteristics
2Area of stationary object
If smoke detectors are used for fire detection, then the detection coverage is broad, but the response time increases
Solution Approach 1:
The patent detects UV radiation from flames at the instant of ignition rather than waiting for smoke to accumulate and reach the detector. This parameter change from detecting combustion products (smoke) to detecting UV radiation enables near-instantaneous response while maintaining broad detection coverage
Solution Approach 2:
The patent replaces the mechanical/chemical detection mechanism of smoke detectors with an optical detection mechanism using a Schottky-barrier diode. This substitution enables faster response by directly detecting UV photons from flames without requiring smoke accumulation or mechanical movement
3Area of stationary object
If conventional detectors are used in car parks, then the detection coverage is adequate, but false alarms occur due to exhaust fumes
Solution Approach 1:
The patent changes the detection wavelength to the solar-blind UV region (220-280 nm), where exhaust fumes have no significant absorption or emission characteristics. This parameter change eliminates interference from exhaust fumes while maintaining adequate detection coverage in car park environments
Solution Approach 2:
The patent exploits the fact that exhaust fumes are transparent in the UV solar-blind region while flames emit strongly in this region. By selecting this specific wavelength range, the detector converts the presence of exhaust fumes from a potential interference into a non-issue, as they do not absorb or emit UV radiation at these wavelengths
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 UV radiation detector achieves a sharp cutoff at 235 nm with over 5 orders of visible rejection and external quantum efficiency of up to 19%, providing reliable and rapid fire detection with minimal false alarms and durability against water vapor, suitable for solar-blind UV flame detection applications.
Implementation Method 1
Able to compensate for some of the above disadvantages of smoke detectors, flame detectors have recently attracted much research and development attention. Flame detectors use optical sensors working at specific spectral ranges to record the incoming radiation at the selected wavelengths.
Implementation Method 2
A UV radiation detector using a Schottky-barrier diode with a rocksalt phase crystalline structure of CaS or CaTe as the active layer
Implementation Method 3
growing a binary molecular precursor layer on a substrate. In the growth process, the substrate is heated to a first temperature, then molecular beam epitaxy is conducted on one side of the substrate
Implementation Method 4
molecular beam epitaxy is conducted on one side of the substrate
Data Source
AI summary
A UV radiation detector includes: a diode including a substrate having a first side and a second side, the first side and the second side being located on opposing faces of the substrate, an active layer including rocksalt phase crystalline structure CaS disposed on the first side of the substrate, an electrical contact disposed on the second side of the substrate, and a semi-transparent conducting layer disposed on the active layer; and a circuit connecting the semi-transparent conducting layer and the electrical contact. The UV radiation detector detects radiation having a wavelength between 200 and 280 nm.