Search

Maskless phase-change lithographic technology is developed as a photoresist of phase-change materials. The controllable growth behavior of the crystallization region on an amorphous thin film of Ge2Sb2Te5 (GST) irradiated by a laser beam is investigated; the GST thin film is deposited on a silicon substrate by the sputtering method. The results of a series of the experiments and the simulations all show that the width of a crystalline pattern is not only closely related to laser power and pulse duration, but also is apparently affected by the interactive area between the focused laser spot and thin film. The width maintains a nonlinear growth with the enhancement of the laser power until the thin film approaches melting, whereas it gradually reaches a constant value due to the local thermal equilibrium. This equilibrium makes the width irrelevant to the moving velocity with certain constraints when the laser works in continuous-wave mode. Within a defocus range of 15 µm, the widths of the crystalline patterns are obtained in a broad range from 690 nm to 8.13 µm under a 0.4-NA objective lens. By adjusting the defocus amount, some crystalline square patterns with expected widths in a wide range are fabricated, and the mean percentage error between the expected and fabricated widths is only 1.495%. [ABSTRACT FROM AUTHOR]

A model of an optical disk containing data pits with a range of depths and orientation angles is simulated to investigate how the Stokes parameters of the light reflected from these pits vary. Pits carrying multiple bits of information can be recovered according to the Stokes parameters, particularly S0 and S1, which show different variation trends versus the depth and orientation angles. In addition, the signal width of S0 ceases to be constant, and instead varies as a function of the orientation angle during laser scanning. This can double the available modulation range of the orientation angle and further enhance disk storage densities. [ABSTRACT FROM AUTHOR]