How to influence silicon substrates gas sensor conduction.some people use normal glass slide to study gas sensor property. why use glass slide and silicon substrates.
Here why use conducting and non conducting substrates.And which substrate give good gas sensing property?
Difficult question(s) ...
Some aspects
- Glass slides are easily available in good quality. If the sensor production process is low temperature, they can be used - even if it is difficult to produce reliable contacts. Glass slides will mostly be found in very early prototyping stages, normally not in series production.
- Another alternative is Al2O3 ceramics. Not so easily obtained. If you need high temperature processes during production, these ceramics are a non-conductive alternative.
- Silicon is quite universal. To assume, that silicon is used due to conductive properties may be misleading. I personally had a project where we 'ended up' with silicon. Not due to the conductive properties (we had an isolation layer as the foundation of our sensor buildup) but due to the processing requirements: these were only available from semiconductor fabs that are only prepared to process 'things' built on semiconductor wafers. Thus the silicon.
- When it comes to series products, silicon eventually allows for integration of the evaluation circuitry. Though the gas sensing element normally has nothing to do with the silicon, you are free to integrate the circuitry underneath the sensing element.
Reading 'substrate' in it's basic meaning 'carrier' helps :)
It will always be carrier, sometimes in addition 'functional element'.
Oh - the last question: The substrate has nothing to do with sensing properties in all gas sensors I know. (Which is quite a number.)
Wish you success.
Thank you very much U. Dreher. your answer is most useful for me.
Glass slides are non conducting substrates: If the deposited material on the substrate is conducting or semiconducting then substrates plays an important role of conduction of electron. As we know gas sensing is a electrochemical process i.e. gas is interacted with coated material and hence electrons flows through the coatings but electron always chooses a path of minimum resistance and hence if substrate is non conducting then electron flows only through the coating material not through the substrate. If substrate is conducting then electron will flow through substrate instead of coating materials. And hence we are unable to record the exact result from only coating materials.
@ Amarnath Marimuthu
If you mean "create traces" by the word "coat": there's quite a number of options (just starting with sputtering) to deposit an initial (conducting) layer adhering to the glas. From this point on, you're in the domain of "classical" layer upbuild.
You may e.g. lookup LCD production (which is starting with some glass substrate these days) to get an impression of the plentitude of steps available.
Hope this helps ...
Thank you sir. But i am asking just how to simply stick my material on the normal glass slide to take the sensing activity. to measure the resistance change. I have my sample in powder form is there any conducting pastes or any solvents which can be dispersed or mixed to place on the surface of the glass slide. and one more think it should not be conducting material thus the changes should be within the sampole itself.
Oh :)
The usual buildup of these sensors is to build a conducting structure (the "electrodes") on the glass surface. If your sensing material is in powder form, you'll have to process it to some thick slurry (e.g. mixing with some volatile component like some alcohol) and deposit a "drop" of this slurry to the sensing area of the electrodes. Heating this assembly would evaporate the volatile component, subsequent tempering might be able to reduce the starting resistance of your sensing material.
On RG you might find some threads about "interdigitated electrodes", MOx sensors etc. Beyond that, google might be of some help. I'm quite sure that there are some patents depicting the overall setup of such sensor assemblys, eventually giving away some basic steps of the production.
(I myself have been working with a manufacturer of such assemblies who is quite good in manufacturing these assemblies. But I am not allowed to go too much into the details.)
This is not the case, as lot of research on gas sensor is carried on other substrates like polymer and LTCC etc. It depends upon the thickness of the sensing film also and eventually the conduction mechanism as stated by J.V. Thambore.
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