i have an FTO layer on substrate glass , how can i connect the circuit and measure the hall constent and electron concentration
Sherif, FTO (SnO2:F) is one of the easiest materials to do a Hall measurement on. However, you will need to know the thickness. The doping concentration is nearly always degenerate (surface space charge width narrower than needed for a tunneling contact), so ohmic contacts are easy (usually 4 very small indium metal dots, pressed onto the opposite edges of the sample surface with the flat side of a metal tweezers - are fine, no heat treatment necessary). Actually, for most commercial Hall systems with spring-loaded contacts, you can usually just place the spring contact near the edges the FTO surface, and the contact will be good enough. For the Van der Pauw method, and contact areas < ~0.5 mm2, usually use a sample about 1 cm x 1 cm - much smaller samples will yield increasing larger errors in the mobility. For commercial FTO, expect electron mobilities no greater than ~30 cm2/V-s, and possibly
FTO is a very intensively investigated and used in many devices TCO. Check the literature for that.
You firstly need to make ohmic contacts on the thin films. You may check the literature for appropriate metal and ohmic contact formation method for your thin films.
You may use the Hall bar geometry or Van der Pauw measurement to determine carrier concentration then. You need a multimeter to measure/apply current and voltages through the contacts and a magnet to apply the magnetic field. The magnetic field range in which the Hall measurement are most accurate could be found from literature.
Details of a type of measurement are explained at (https://www.nist.gov/pml/engineering-physics-division/popular-links/hall-effect/hall-effect-figure-3)
Sherif, FTO (SnO2:F) is one of the easiest materials to do a Hall measurement on. However, you will need to know the thickness. The doping concentration is nearly always degenerate (surface space charge width narrower than needed for a tunneling contact), so ohmic contacts are easy (usually 4 very small indium metal dots, pressed onto the opposite edges of the sample surface with the flat side of a metal tweezers - are fine, no heat treatment necessary). Actually, for most commercial Hall systems with spring-loaded contacts, you can usually just place the spring contact near the edges the FTO surface, and the contact will be good enough. For the Van der Pauw method, and contact areas < ~0.5 mm2, usually use a sample about 1 cm x 1 cm - much smaller samples will yield increasing larger errors in the mobility. For commercial FTO, expect electron mobilities no greater than ~30 cm2/V-s, and possibly
Better use Van der Pauw method with standard clover geometry and 4 dot metalization contact areas < ~0.5 mm2, we have to know the thickness and effective film area involve in magnetic flux, then hall voltage and hall constant from hall effect measurement, also need information film conductivity, finally use appropiate formula the concentration and mobility can be calculated. Also I agree with Timothy Gessert
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