User:Floriane Briere/Notebook/CHEM-496/2011/10/11

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Objective

We prepared all the materials to perform a four probe method. This method will allow us to determine the resistivity of the filaments we obtained after our first Gold NPs syntheses.

To measure the resistivity of a material, two methods can be use. Each of them permit to perform absolute measurement without using calibrated standards:

  1. The two-probe method: it uses 2 probes (the manipulation is easier but the datas' interpretation is harder); each contact serves as a current and and as a voltage probe.
  2. The four-probe method: it uses 4 probes (the manipulation is harder but the datas' interpretation is easier). There are:
    1. Two outside probes (1 and 4) which induce a current through the actuator; the actuator owns its own resistance so when the current is flowing through it, there would be a voltage drop.
    2. Two inside probes (2 and 3) which are connected to a voltmeter; it permits to measure the voltage drop. The actuator’s resistance is equal to the voltage measured using voltmeter divided by the known current applied to the actuator.

References:

  • Semiconductor material and device characterization, third edition, by Dieter K. Schroder (2006)
  • Experimental investigation of MEMS thermal actuator displacement under shock, by Ming Hung Hung

Protocol

  1. Prepare four rectangular Paladium foils (which will be stucked from left to right):
    1. Number 1: 4.8mm x 6.3mm (= 30.2mm²)
    2. Number 2: 2.3mm x 7.4mm (= 17mm²)
    3. Number 3: 2.2mm x 7.4mm (= 16.8mm²)
    4. Number 4: 3mm x 7.5mm (= 22.5mm²)
  2. Cut four Paladium wire (each of about 1.5cm length)
  3. Stick each foil to one wire using conductive Epoxy; dry the Epoxy by using a heat gun.
  4. Stick the four Paladium compounts to a Teflon sheet (about 3cm x 3cm); the different foils and wires must not touch each other and they have to be as closed as possible.

We notice that the foils 2 and 3 have to have an area as closed as possible; the foils 3 and 4 will be used as references. At the end, the four Paladium compounts must not be in contact between each other (neither by direct contact; neither through the Epoxy).

Conductive Epoxy (Chemtronics) is a silver compount which provides excellent electrical conductivity and high thermal conductivity; we are using it to make high-strength solderless conductive connections.



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