Electrical Properties of Metals and Semiconductors (My Own's)

Electrical properties of metals and semiconductors
Aryan GHOTBI 081122110

We aim to acquire measurement techniques of electrical properties and gain a better understanding of electrical properties of substances.
We choose 3 types of substance having remarkably different electrical properties. Two metal samples of Cupper (99.99%) and Ni-B-Si amorphous alloy; and Germanium (99.999%) as a semiconductor sample. Then we measure temperature change of their electric resistance in a temperature range from room temperature to 200˚C.
Preliminary Introduction:
We want to understand electrical properties of our given substances. From Ohm’s law we only find the relationship between voltage and current from a constant resistance. We do not derive any solid state properties of a material from R in that formula. In this case we have to look at the properties that affect resistance according to:
R =ρ LS
In order to set up an experiment for measuring the resistance, we used the DC 4 terminal method. In this method, voltmeter is separated from the current by having a very high internal resistance (Ip). We first were given an established circuit wiring according to figure below taken from the manual book. Our experiment follows two steps: 1) Measuring resistivity at room temperature. 2) Measuring temperature dependence of electric resistance.  
Experiment and method:
First Step: We set the knob of the constant voltage power source to zero, and then turn the voltage knob to set the current flowing through each samples to 3mA. We calculated the current value (I) by the formula
I = E0r0 → I=83.41÷27.82= 3 A
(Where r0 is resistance of the reference resistor and E0 is the voltage across the reference resistor). We also measured EX(Ge), EXCu and EX(Ni-B-Si) in millivolts across the samples with the multimeter and obtained resistance in ohms as follows:
EX(Ge)=0.853, EXCu=4.52, EXNi-B-Si=5.22
r1=284.3, r2=1.506, r3=1.74
We then calculated the resistivity...