Nanostructured Lanthanum Oxide Sensor for Fast Humidity Detection
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Solution Overview
Problem
Existing humidity sensors, particularly capacitive-based metal oxide semiconductor (MOS) sensors, have slower response times and complex, expensive readout circuits, making them less desirable for applications requiring fast and accurate moisture detection.
Innovation Solution
A thin-film gas sensor device with a nanostructured layer formed from lanthanum oxide, using atomic layer deposition (ALD) on a non-suitable seed layer, which increases hole density in response to target gases like water vapor, reducing electrical resistance within a time constant of less than one second, and featuring a simpler resistance-based readout circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If capacitive-based MOS humidity sensors with organic polymer are used, then the sensor can detect humidity changes, but the response time is slower than desired
Solution Approach 1:
The patent changes the material parameter from organic polymer to inorganic metal oxide (lanthanum oxide), and changes the structural parameter from thick-film to thin-film nanostructured. This material and structural transformation enables faster response time (less than one second) while maintaining detection accuracy through the material's inherent semiconductor properties and increased surface area-to-volume ratio in the thin-film configuration.
Solution Approach 2:
The patent replaces the capacitive-based detection mechanism with a resistive detection mechanism. Instead of measuring capacitance changes in organic polymer, the invention uses resistance changes in inorganic metal oxide thin-film, which responds faster to humidity changes while providing equivalent or superior detection accuracy.
2Ease of manufacture
If capacitive-based MOS humidity sensors are used, then humidity detection is achieved, but the external readout circuit is complex and expensive
Solution Approach 1:
The patent substitutes capacitive sensing with resistive sensing, which uses simpler readout circuits. The resistance change in the thin-film metal oxide can be directly measured with basic ohmmeter circuits, eliminating the need for complex capacitance measurement circuits required by organic polymer-based sensors.
Solution Approach 2:
The patent employs a thin-film structure that can be manufactured using cost-effective deposition techniques, replacing the more expensive thick-film capacitive sensors. The simplified circuit requirements further reduce overall system cost.
3Speed
If thick-film MOS gas sensor is used, then the gas-sensitive portion can undergo change in optical transmittance and ionic conduction, but the response time is slower than desired
Solution Approach 1:
The patent transitions from three-dimensional thick-film structure to two-dimensional thin-film structure with reduced thickness. This dimensional reduction increases the surface area-to-volume ratio, enabling faster gas diffusion and response time while requiring precise thickness control during fabrication.
Solution Approach 2:
The patent changes the physical parameter of film thickness from thick to thin configuration, and transforms the material from organic polymer to inorganic metal oxide. These parameter changes enable faster response time while the thin-film deposition process provides precise thickness control.
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 sensor provides a fast response time, improved sensitivity, and reduced complexity and cost compared to traditional sensors, with a non-organic material that is more robust and efficient, suitable for various applications.
Implementation Method 1
The semiconductor material is configured to undergo an increase in a density of the holes in the presence of a target gas, thereby decreasing an electrical resistance of the nanostructured thin film layer
Data Source
AI summary
A thin film gas sensor device includes a substrate, a nanostructured thin film layer, and a first and a second electrode. The nanostructured thin film layer is supported by the substrate and is formed with a semi-conductor material including holes. The semiconductor material is configured to undergo an increase in a density of the holes in the presence of a target gas, thereby decreasing an electrical resistance of the nanostructured thin film layer. The first and the second electrodes are supported by the substrate and are operably connected to the nanostructured thin film layer, such that the decrease in electrical resistance can be detected.