Oriented thin films of p-nitrophenyl nitroxyl nitroxide radical

Thin films (thickness similar to 2 mu m) of the molecular organic radical p -nitrophenyl nitroxyl nitroxide (p-NPNN) have been obtained by evaporating different crystallographic phases (alpha, beta and gamma) of the p-NPNN pre cursor in vacuum on glass and cleaved NaCl(001) substrates. The films cryst allize in the alpha-phase (monoclinic) and show a high degree of orientatio n of the c*-axis perpendicular to the substrate, independently of the precu rsor phase. The films undergo a spontaneous phase transition, from alpha to beta, under certain conditions.