Analyzing this data gives us information on how the electronic properties of this material vary with thickness. Many other factors play into these measurements, including human errors in the measurements, contact resistances, and the behavior of the device under certain atmospheric conditions.
Measurements Performed.
A multimeter was used to make the majority of the current measurements and a voltage source to adjust voltage. The setup is the positive voltage source to the positive lead of the two point probe. The positive lead of the two-point probe contacts the ZnO part of the ZnO-ITO device, and the negative lead is in contact with the ITO causing the tunneling electrons that move to the conductance band and cause the semiconductor to start conducting like a metal. The negative lead then leads to the positive current port of the multimeter which takes the current reading. The current reading is taken in milliamps and is displayed on the multimeter screen and is recorded manually or through the NI program on the computer. The lead then goes from the COM ports on the multimeter to the negative lead of the voltage source, completing the circuit. .
It is important to visually observe the contacts closely, and make sure a good connection is made without bending the tips. The tips of the probe must also be completely on their respective materials or else the reading may not be accurate. We took a total of 6 measurement from 6 different points of the material to get a behavior of the device over different thicknesses of the ZnO. The measurements starts from zero voltage and rises by 1/10 of a voltage until the voltage source reads five voltage. We set the ampere limiter to one amp due to the fact that we need accurate readings within the range of our reader and do not want to blow the fuse of the multimeter. Errors can occur with the contact resistance, vibrations, and one big error can occur with the ZnO nanoparticles moving due to contact with the probe which can change the voltages taken dramatically.