Thin Colloidal Crystals

Colloidal crystals, made of large polystyrene particles (1.1 pm in diameter), are confined into a thin layer between two glass boundaries. When the thickness h of the layer is increased progressively from zero, a sequence of structures S(h) is detected from direct observations in an optical microscope. These structures are stacks of n square ( )—or triangular (A)ordered layers F.or n ~ 7, the sequence S(h) is. . .nA-(n + 1) -(n +])~-.. . .