Studies of pulsed laser melting and rapid solidification using amorphous silicon

Conference · Fri Jun 01 04:00:00 EDT 1984

OSTI ID:6677828

Lowndes, D H; Wood, R F

Pulsed-laser melting of ion implantation-amorphized silicon layers, and subsequent solidification were studied. Measurements of the onset of melting of amorphous silicon layers and of the duration of melting, and modified melting model calculations demonstrated that the thermal conductivity, K/sub a/, of amorphous silicon is very low (K/sub a/ approx. = 0.02 W/cm-K). K/sub a/ is also the dominant parameter determining the dynamical response of amorphous silicon to pulsed laser radiation. TEM indicates that bulk (volume) nucleation occurs directly from the highly undercooled liquid silicon that can be prepared by pulsed laser melting of amorphous silicon layers at low laser energy densities. A modified thermal melting model is presented. The model calculations demonstrate that the release of latent heat by bulk nucleation occurring during the melt-in process is essential to obtaining agreement with observed depths of melting. These calculations also show that this release of latent heat accompanying bulk nucleation can result in the existence of buried molten layers of silicon in the interior of the sample after the surface has solidified. The bulk nucleation implies that the liquid-to-amorphous phase transition (produced using picosecond or uv nanosecond laser pulses) cannot be explained using purely thermodynamic considerations.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6677828
• Report Number(s): CONF-840775-1; ON: DE84014737
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
AMORPHOUS STATE
ELEMENTS
HEATING
ION IMPLANTATION
LASER-RADIATION HEATING
LAYERS
MELTING
NUCLEATION
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PLASMA HEATING
SEMIMETALS
SILICON
SOLIDIFICATION
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES