What is the effect of temperature on nanomeasurements?

Thermal voltages or EMFs are the most common source of error in low voltage measurements [1]. These voltages are generated when different parts of a circuit are at different temperatures and when conductors made of different materials are connected together, as shown in Figure 5. The Seebeck [2] coefficients of various materials relative to copper are listed in the table.
 

 
Figure 5: Thermal voltages are generated when different parts of a circuit are at different temperatures and when conductors made of different materials are connected together.
 
The generation of thermal EMFs [3] can be minimized by making all conductors in the circuit out of the same metal. For example, a connection made with a crimped copper sleeve or lug to a copper wire creates a cold-welded copper-to-copper junction that generates very little thermal EMF. In addition, the connection must be kept clean and free of oxides. For example, the Seebeck coefficient for a clean Cu-Cu connection is ±0.2mV/°C, while the Seebeck coefficient for a Cu-CuO connection is as high as 1mV/°C.                                                                    
 

Paired Material	Seebeck Coefficient, QAB, microvolts/°C
Cu-In	<0.2
WITH their	0.3
Cu-Pb/Sn	1–3
with his	400
Cu-CuO	1000

Minimizing the temperature gradient in the circuit can also reduce the thermoelectric EMF. A technique to reduce this gradient is to keep all connection points as close as possible and to achieve good thermal coupling to a common, large heat sink.[4] Electrical insulation materials with high electrical conductivity must be used, but since most electrical insulators do not conduct heat well, specialized insulators such as hard anodized aluminum, beryllium oxide, specially filled epoxy, sapphire, or diamond must be used to connect each connection point to the heat sink.[5] In addition, allowing the test equipment to complete a warm-up period and reach thermal equilibrium at a constant ambient temperature can also minimize the effects of thermoelectric EMFs. Some instruments even provide various built-in measurement modes that change the polarity of the test signal to cancel the thermal EMF.