Mechanical

Question 1

Mechanisms for the change in resistance of silicon under mechanical stress

Answer 1

Shape of elipsoids for the minimum energy in the conduction band change under stress, the anisotropy is gone -> rearrangement of electrons in the minima

Question 2

Two accelerometer structures

Answer 2

-lateral accelerometer
- you can use cantilevers and the piezoelectric effect
-Typical accelerometers or acceleration sensors are based on a piezoelectric crystal placed between two capacitor plates, which is fastened to a mass. When the device is accelerated the mass presses on the
crystal generating a small voltage on the plates which is a measure for the acceleration. An advantage of these devices is that they are self generating
and do not require an external power supply.

Question 3

Where to put piezo resistors in pressure sensors and n or p type silicon for the resistors

Answer 3

• use p type silicon

Question 4

Read out techniques for mechanical sensors

Answer 4

• piezoelectric - current or voltage
• capacitive - deflection of the diaphragm
• piezoresistive - resistance

Question 5

Working principle of a gyroscope

Answer 5

Coriolis effect, measure rotational forces

Question 6

p or n type silicon for the piezo resistors?

Answer 6

p-type silicon, still not sure why, but I think the piezoresistive effect is much higher

Question 7

Polycrystalline Silicon

Answer 7

Material composed of small grains of silicon crystal s, often showing some texture separated by grain boundaries.

Question 8

two ways piezoelectric can be used in mechanical sensors

Answer 8

• cantilever

- accelerometers