Printable inks with silicon/germanium based nanoparticles with high viscosity alcohol solvents
Silicon based nanoparticle inks are formulated with viscous polycyclic alcohols to control the rheology of the inks. The inks can be formulated into pastes with non-Newtonian rheology and good screen printing properties. The inks can have low metal contamination such that they are suitable for forming semiconductor structures. The silicon based nanoparticles can be elemental silicon particles with or without dopant.
1. A nanoparticle ink comprising from about 0.001 weight percent to about 30 weight percent silicon/germanium based nanoparticles, at least about 10 weight percent of a viscous polycyclic alcohol, wherein the viscous polycyclic alcohol has a boiling point of no more than about 450° C. and non-Newtonian rheology.
2. The nanoparticle ink of claim 1 wherein the viscous polycyclic alcohol has 7-25 carbon atoms.
3. The nanoparticle ink of claim 1 wherein the viscous polycyclic alcohol comprises a norbornyl bicyclo moiety.
4. The nanoparticle ink of claim 1 wherein the viscous polycyclic alcohol is selected from the group consisting of vinylnorbornyl alcohol, C-8 substituted 1,5-dimethyl-bicyclo[3.2.1]octane-8-ols with ethyl, methyl, n-propyl, i-propyl, n-butyl, 1-methyl-propyl, 2-methyl-propyl, allyl, n-hexyl, 3-methyl butyl, cyclopentyl or cyclohexyl substitutions, isobornyl cyclohexane diol, trimethyl-2,2,3-norbornyl-5-(-3-cyclohexanol-1), 3-(5,5,6 trimethyl bicyclo[6.4.0.1]heptan-2-yl)cyclohexanol, 11-hydroxy-2,13,13-trimethyl-tricyclo[6.4.0.1 2,5 ]tridecane and combinations thereof.
5. The nanoparticle ink of claim 1 further comprising no more than about 0.1 weight percent polymer.
6. The nanoparticle ink of claim 1 further comprising no more than about 100 ppb transition metal contamination.
7. The nanoparticle ink of claim I wherein the silicon/germanium based nanoparticles comprise doped elemental silicon nanoparticles having an average primary particle size of no more than about 50 nm.
8. The nanoparticle ink of claim 1 comprising at least about 0.5 weight percent elemental silicon nanoparticles and having a viscosity of at least about 1 Pa·s at a shear of 2 s −1 .
9. The nanoparticle ink of claim 1 wherein the nanoparticles have a dopant level of at least about 0.5 atomic percent.
10. The nanoparticle ink of claim 1 comprising vinylnorbornyl alcohol, C-8 substituted 1,5-dimethyl-bicyclo[3.2.1]octane-8-ols with ethyl, methyl, n-propyl, i-propyl, n-butyl, 1-methyl-propyl, 2-methyl-propyl, allyl, n-hexyl, 3-methyl butyl, cyclopentyl or cyclohexyl substitutions, isobornyl cyclohexane diol, trimethyl-2,2,3-norbomyl-5-(-3-cyclohexanol-1), 3-(5,5,6 trimethyl bicyclo[6.4.0.1]heptan-2-yl)cyclohexanol, 11-hydroxy-2,13,13-trimethyl-tricyclo[6.4.0.1 2,5 ]tridecane and combinations thereof and having a transition metal contamination of no more than about 100 ppb.
11. The nanoparticle ink of claim 1 having from about 0.1 weight percent to about 20 weight percent silicon nanoparticles.
12. The nanoparticle ink of claim I having from about 20 weight percent to about 80 weight percent polycyclic alcohol.
13. The nanoparticle ink of claim 1 having from about 30 weight percent to about 80 weight percent polycyclic alcohol.
14. The nanoparticle ink of claim 13 further comprising terpineol.
15. The nanoparticle ink of claim 1 further comprising terpineol.
16. The nanoparticle ink of claim 1 further comprising no more than about 0.1 weight percent solvent boiling below 165° C.
17. The nanoparticle ink of claim 1 having a ratio of the viscosity at a shear of 2 s −1 to the viscosity at a shear of 1000 s −1 from about 2.5 to about 50.