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JDRF85
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Hi everyone
This is my first post, please be kind!
I am part of a research group at Oxford University, UK. We are investigating ways to make multicrystalline Si solar cells more efficient. One of the characterisation techniques we use is electron beam induced conductivity (EBIC) measurement, which is a scanning electron microscopy technique.
To use the EBIC technique, we have to make a Schottky contact on the top surface of the sample mc-Si wafer (surface exposed to electron beam), and an Ohmic contact on the back. Ohmic contact is made with high-purity liquid metal alloy of Indium and Gallium (InGa alloy) applied to wafer surface, then a layer of "silver-dag" is painted on and used to affix sample to copper stub that then goes into SEM. SEM vacuum is approximately 10^-7 Torr.
Here is my problem: I want to know whether the InGa alloy, which is liquid at room temperature and atmospheric pressure, will evaporate at room temperature and 10^-7 Torr pressure. If it does, then we cannot use the technique, since we do not want the inside of the SEM to become coated with evaporated InGa!
I cannot find data for enthalpy of vaporization of InGa alloy. This led me to consider in general terms, the problem of evaporation of liquid metal alloys. I cannot find any answers to the questions:
1) Can 2-component liquid-metal alloys evaporate eg InGa (l) --> InGa (g)?
2) If answer to 1 is "yes", then how does this occur?
3) If answer to 1 is "no", do liquid-metal alloys remain liquid at low pressures? If not, then how do they evaporate?
4) Can one calculate enthalpy of vaporization of alloy using enthalpies of vaporization of components and Gibbs energy of mixing, and if so, how?
I have been looking at the literature all afternoon and am at a loss. Any help will be greatly appreciated.
Thanks for taking the time to read my question!
Johnny
This is my first post, please be kind!
I am part of a research group at Oxford University, UK. We are investigating ways to make multicrystalline Si solar cells more efficient. One of the characterisation techniques we use is electron beam induced conductivity (EBIC) measurement, which is a scanning electron microscopy technique.
To use the EBIC technique, we have to make a Schottky contact on the top surface of the sample mc-Si wafer (surface exposed to electron beam), and an Ohmic contact on the back. Ohmic contact is made with high-purity liquid metal alloy of Indium and Gallium (InGa alloy) applied to wafer surface, then a layer of "silver-dag" is painted on and used to affix sample to copper stub that then goes into SEM. SEM vacuum is approximately 10^-7 Torr.
Here is my problem: I want to know whether the InGa alloy, which is liquid at room temperature and atmospheric pressure, will evaporate at room temperature and 10^-7 Torr pressure. If it does, then we cannot use the technique, since we do not want the inside of the SEM to become coated with evaporated InGa!
I cannot find data for enthalpy of vaporization of InGa alloy. This led me to consider in general terms, the problem of evaporation of liquid metal alloys. I cannot find any answers to the questions:
1) Can 2-component liquid-metal alloys evaporate eg InGa (l) --> InGa (g)?
2) If answer to 1 is "yes", then how does this occur?
3) If answer to 1 is "no", do liquid-metal alloys remain liquid at low pressures? If not, then how do they evaporate?
4) Can one calculate enthalpy of vaporization of alloy using enthalpies of vaporization of components and Gibbs energy of mixing, and if so, how?
I have been looking at the literature all afternoon and am at a loss. Any help will be greatly appreciated.
Thanks for taking the time to read my question!
Johnny