Dear Sinan,

Have you made some devices on your film structure? Please let me know.

If you have fabricated some devices then I may assist you about 1/f noise measurement.

Thank you.

If you need this info for VOx based bolometer, you can extract voltage noise per frequency bandwidth Vn/sqrt(Df) by measuring responsivity Rv of the bolometer ( i.e. the output signal voltage per incident IR power) and its detectivity D as a function of bias current and chopper frequency. These three parameters are related as follows: sqrt(Ad)*Rv/D=Vn/sqrt(Df), where Ad is the area of the detector.

Dr. Dixit & Prof. Sergeenkov,

We grow VOx films on Si/SiO2 substrate without any lithography process. We have a AC/DC source generator and a nanovoltmeter. Can we make 1/f noise mesaurement with these equipment?

I am planning to achive noise with analyzing the fluctuations on the film, is this the right way? Also I can't decide which current type ( AC or DC ) I should use for the measurement.

Thanks for your help.

Prof. Sergeenkov,

As mentioned in the previous comment we have only a AC/DC source generator and a nanovoltmeter. In the literature, 1/f measurements are conducted with the fluctuations on a current at low frequency, is it possible to make it that way with our equipments?

Secondly bolometers work with DC current, so should I make the analysis with DC current? If it is so, how I can I define the DC current in terms of frequency?

My plan is as follows:

1) Applying AC (low frequency, 0.1-1 kHz) and Pulsed DC current to the thin film.

2) And then I will analyze the fluctuations (i.e.at 5 Hz, 10 Hz. 15 Hz. etc.) in the data gathered by the nanovoltmeter.

I don't have the necessary information about the chopper frequency, what is its definitiıon and how do I apply it to our system?

Thank you very much for your attention and help.

Dear Sinan,

As you have mentioned that you have not processed your sample with lithography, then how will you make top and bottom contacts on your device?

Without patterning the contacts, how is it possible to make the current flow through your device? With no patterns on the film, the contacts will simply shorted.

Also as you want to study 1/f noise spectrum of your sample (means behavior of noise signal with frequency), as far as my information is concerned, AC current is required as DC has no frequency dependance.

Thank you.

By "without any litography" I meant the actual process is not carried out but we have used a simple litography process (coating with gold and then etching) for contacts. Thank you for your advice on current type.

Should I follow a stepwise approach for the fluctuations, I mean should I analyse the fluctuations per Hertz (i.e.at 1 Hz, 2 Hz. 3 Hz. etc. each for 5 seconds)?

Yes, a stepwise approach seems reasonable in your situation. However, there is no guarantee that you will actually measure 1/f (Flicker) noise in your films this way because voltage fluctuations can be caused by many different reasons. Still, I think it's worth trying. But, in addition, you must test your sample with DC current as well. The measured current-voltage curves (for different temperatures, if possible) will give you a clue about the quality of your sample and the attached gold contacts. Temperature dependence of the resistivity is a powerful tool. This step is important for the correct analysis of the obtained fluctuations spectrum.

You can also vary the bias voltage and can observe the effect on 1/f noise. as you might be aware that 1/f noise is prominent in the low frequency range so observe the low frequency spectrum carefully. I also advise you to go through the literature survey on 1/f noise measurement, that will be very helpful for you (please find one review paper in attachment).

Thank you.