A method is provided for preparing an etching mask on a substrate. The method includes dispersing a plurality of particles in an aprotic suspending medium to form a suspension and spin-coating the suspension on a substrate to form an etching mask on the substrate.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 This invention was made with government support under 1041895 awarded from the National Science Foundation and the Department of Energy. The United States government has certain rights in the invention.