Thank you very much Dr Löper,
I will check the papers asa soon as possible.
Best,
Zeynep
Dear Volker,
Thanks a lot. You are right,For now, I need a general overview for this topic.
@ Zeynep: Pure amorphous Si to single crystal transformation happens at 550 degrees C at a rate about 0.1nm per second. (crystal growth is a thermally activated process, the higher the temperature the faster the groth.) My number is obtained from Solid State epitaxy experiments. Namely, ion implantation damage a single crystal Si wafer ( just like the case in Ion Implantation in the microelectronics fabrication) , and watch its annealing at a given temperature to restore back into single crystals.
Results show at 500-550C growth startes. Silicon device fab labs use higher temperature (950-1100C), because they want to get rid of the line defects in Si wafers.
With other agitation (such as radiation), the temperature could be as low as 200-300C).
The answer to your question depends on what is your silicon nanoparticles ? If they are high purity amorphous Si atoms, they will become crystalline easily as I stated. If they have impureties, answer will be very much different.
I would not expect much diffusion below the Silicon brittle to ductile transition temperature. This temperature depends on defect/impurity concentrations . If the nanoparticles are pure one could expect significant hysteresis above that temperature. In an older paper (Fracture Mechanics of Ceramics editor Bradt 1983) I have calculated this temperature using corresponding states for a range of diamond and sphalerite structure solids. Depending on the dislocation density from 0 to 200 disloc/sqcm the Si brittle to ductile calc. temp ranges from ( 555C to 726C) and the collected experimental data (600-780C). WeiKan's estimate for high defect density provides a lowest Temp ballpark no and the brittle to ductile approach indicates a somewhat higher temp. for very pure materials with minimal if any defects.
Dear Robert,
Thanks a lot.
Each info is important for me, still trying to understand ..
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructures
- Thin Films