![]() A germanium atom travels approximately 0.29 nm from an octagonal to a tetragonal site in this process. Kolobov, et al., is distinct from highly disordered amorphization. The displacements of Ge atoms, referred to as local amorphization 9 by A.V. Time-resolved x-ray spectroscopy has suggested that the amorphization of GST is initiated by the displacement of Ge atoms from an octahedral to a tetrahedral arrangement 15. Time-resolved optical studies have demonstrated that the optical index of GST changes from opaque to transparent within 1 ps after near-infrared (IR) photoexcitation, with a clear threshold in the fluence of the incident laser for permanent amorphization 12, 13. The dynamics of this ultrafast phase transition in GST has been studied using time-resolved spectroscopy 12, 13, 14, 15 and x-ray and electron diffraction 16, 17. ![]() Recently, a nonthermal phase transition of the Ge 2Sb 2Te 5 (GST) poly-crystal or the GeTe–Sb 2Te 3 superlattice by an ultrashort pulsed laser has been proposed, which may realise ultrafast memory encoding 9, 10, 11. As the Internet requires faster and denser devices, the key challenges in phase-change memories, such as improving memory access, encoding speed and understanding phase transition and damage mechanisms, should be addressed. The phase transitions in this class of materials are usually induced by nanosecond or continuous-wave lasers via thermal processes involving melting and quenching of the crystal-to-amorphous transition with subsequent annealing to recover the original crystalline phase. Among optical media materials, chalcogenide glasses have several advantages, including a high writing speed (~10 ns bit –1), direct overwriting capability (10 6 cycles) and resistance to climate and natural light 5, 6, 7, 8. One of the major applications for laser-induced solid-to-solid phase transitions is nonvolatile optical storage devices, i.e., phase-change memories: such as compact discs, digital versatile discs and Blu-ray discs 1, 2, 3, 4. Above the fluence threshold, we found that the permanent amorphization caused by multi-displacement effects is accompanied by a partial hexagonal crystallization. The experimental results present a nonthermal crystal-to-amorphous phase transition of Ge 2Sb 2Te 5 initiated by the displacements of Ge atoms. Here we performed ultrafast time-resolved electron diffraction and single-shot optical pump-probe measurements followed by femtosecond near-ultraviolet pulse irradiation to study the structural dynamics of polycrystalline Ge 2Sb 2Te 5. Recent studies have suggested the potential of nonthermal phase transitions in the chalcogenide glass material Ge 2Sb 2Te 5 triggered by ultrashort optical pulses however, a detailed understanding of the amorphization and damage mechanisms governed by nonthermal processes is still lacking. These phase transitions are achieved by laser irradiation via thermal processes. Present in the system.Because of their robust switching capability, chalcogenide glass materials have been used for a wide range of applications, including optical storages devices. The diffraction image represents the scattering of incident radiation,Īnd is useful for identifying translational and/or rotational symmetry DiffractionPattern ( grid_size = 512, output_size = None ) # The API will beįinalized in a future release. When upgrading from version 2.x toĢ.y (y > x), existing freud scripts may need to be updated. The freud.diffraction module provides functions for computing theĭiffraction pattern of particles in systems with long range order.įreud.diffraction is unstable. Benchmarking Neighbor Finding against scipyįĬomputes a 1D static structure factor using the Debye scattering equation.įĬomputes a 1D static structure factor by operating on a \(k\) space grid.Visualizing 3D Voronoi and Voxelization.Calculating the Radial Distribution Function (RDF) from Simulation Data.Handling Multiple Particle Types (A-B Bonds).Using Machine Learning for Structural Identification.Analyzing GROMACS data with freud and MDTraj: Computing an RDF for Water.Analyzing simulation data from HOOMD-blue at runtime.Implementing Common Neighbor Analysis as a custom method. ![]() : Steinhardt Order Parameters from Scratch.
0 Comments
Leave a Reply. |