I am observing an increase in electrical conductivity of my semiconducting material with time, i.e I had tested my samples and initially it gave some value and when I retested the same sample with same conditions after some time its electrical conductivity is increase. is there anyone who has reason or reference for the situation please share.
If the semiconductor sample is chemically and structurally stable, there is no reason to expect a second conductance measurement to give a different result than the former measurement, of course "within the experimental error window".
Therefore, the only chances to get what you have observed are (OR or AND):
1. Your material was not so chemically stable and got modified in the time interval between the two measurements (just consider also that the system is not only the semiconductor but includes also the contacts possibly built on its surface);
2. The measurement setup and procedure has changed (e.g., a better tip positioning may provide a lower conductivity, which by the way would mean that the first measurement involved spurious ohmic paths in series to the semiconductor),
3. The lab environment may have changed so drastically (eg temperature or RH) to sensibly affect the outcome of the measurement... but this point is probably negligible.
dear Younas Iqbal;
The electrical conductivity of semiconducting material depends on the fabricating method but it is a stable property with time. in my opinion, your result of increasing the conductivity with time means than a reaction occurs in the surface of the sample which may be due to the environment led to form a new surface layer with higher conductivity. try to store your sample in an insolated chamber and retest it.
Younas Iqbal In addition to answers Giuseppe Curro Mahmood H. M. At room temperature, the main contribution to the conductivity of a semiconductor will be made by holes formed in the valence band after the transition of valence electrons to acceptor levels, while the probability of the transition of electrons from the valence band to the conduction band will be very small.
Giuseppe Curro your explanation about chemical stability seems to be a valid reason. Mahmood H. M. its also a possibility..., but i have isolated my material from the surrounding. Yuri Mirgord it may also be possible because the material is heated again for the second test for electrical conductivity... Thanks to all for your guidence
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