Action of a laser-induced plane shock wave has been considered as the mechanism of doping of CdTe surface region with In. CdTe crystals coated with a relatively thick In film were subjected to irradiation with KrF excimer laser pulses. The In film was not completely evaporated under irradiation and it served further as an electrode in the fabrication of nuclear radiation detectors. Dopant atoms, implicated by laser-induced stress and shock waves, penetrated into CdTe. An In-enriched region was formed and a built-in p-n junction arose at the depth where a stress wave was converted to a shock wave.

Laser-induced shock wave stimulated doping of CdTe crystals

The structural influences of the laser lift-off (LLO) techniques on the created (0001) GaN surface region are characterized by cross-sectional high-resolution transmission electron microscopy and fitted using the model of stress waves caused by a longitudinal impact at the end of a cylindrical bar extending to infinity. The authors study reveals that, in addition to the superficial damage caused by laser absorption, the stress saltation in GaN crystal where the shock waves come into being induces deformation of the lattices and generates a cluster of half loops above the LLO interface. After that, the lattice deformation will be induced every time the partial dissipation of the steady-state shock waves takes place until the shock wave is dissipated to elastic mode.

Study of the structural damage in the "0001… GaN epilayer processed by laser lift-off techniques

The surface strengthening mechanisms of the 15Kh2MFA(II) heat-resistant steel are analyzed after the laser shock-wave treatment in the air and epoxy resin. The regularities are established in the formation of the ordered surface relief of the steel after treatment. The optical and digital analysis of the surface is performed which allows determining the size of irregularities, taking into account the stochastic and cyclic nature of their formation. The effect of treatment of the 15Kh2MFA(II) heat-resistant steel on the regularities of its static failure is established.

Fracture Mechanism Analysis of the Heat-Resistant Steel 15Kh2MFA(II) After Laser Shock-Wave Processing

A simple technological method is proposed and tested experimentally, which allows for the improvement of mechanical properties in sheet two-phase high-strength titanium alloys VT23 and VT23M on the finished product (rolled metal), due to impact-oscillatory loading. Under impact-oscillatory loading and dynamic non-equilibrium processes (DNP) are realized in titanium alloys, leading to the self-organization of the structure. As a result, the mechanical properties of titanium alloys vary significantly with subsequent loading after the realization of DNP. In this study, the test modes are found, which can be used in the production conditions.

Modification of Mechanical Properties of High-Strength Titanium Alloys VT23 and VT23M Due to Impact-Oscillatory Loading

Profiting by the increasing availability of laser sources delivering intensities above 10 9 W/cm 2 with pulse energies in the range of several Joules and pulse widths in the range of nanoseconds, laser shock processing (LSP) is being consolidating as an effective technology for the improvement of surface mechanical and corrosion resistance properties of metals and is being developed as a practical process amenable to production engineering. The main acknowledged advantage of the laser shock processing technique consists on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly, the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Following a short description of the theoretical/computational and experimental methods developed by the authors for the predictive assessment and experimental implementation of LSP treatments, experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (specifically steels and Al and Ti alloys) under different LSP irradiation conditions are presented

Laser Shock Processing: An Emerging Technique for the Enhancement of Surface Properties and Fatigue Life of High Strength Metal Alloys

The possibility of defect structure and, consequently, strains control using nanosecond laser irradiation-induced shock waves (LSW) both in bulk materials and at the interfaces is investigated. The conditions of the experiment are selected to ensure that the main result of the LSW action would be a change of defect structure at a significantly larger depth in comparison with a thermal influence region. The influence of weak LSW on Fe-Mo and Si–SiO2 interfaces is considered. The potentiality of this technique with respect to the structural quality and residual strains of (Hg, Cd)Te solid solutions due to the LSW interaction with extended defects (low-grain-boundaries, precipitates, etc.) is demonstrated.

Laser shock waves as a tool of changing the strains in materials

Laser-induced shock waves processing of II–VI solid solutions interface

The possibility of defect structure and consequently basic parameters (carrier density, their mobility and lifetimes) control in bulk mercury-cadmium telluride (MCT) using the nanosecond laser irradiation induced shock waves (LSW) is investigated. MCT bulk samples (with composition x equals 0.2) both n- and p- type with different initial structural quality were treated. The post-treatment changes have been detected by galvanomagnetic and photoelectric (lifetime) techniques. Two depending of irradiation mode mechanisms of interaction between LSW and bulk Hg1-XCdXTe defect subsystem are given. The potentiality of this technique as a technological tool for controlled modification of MCT parameters is discussed.

Controling the properties of bulk Hg1-xCdxTe by laser-induced shock waves

The possibility of defect structure and consequently basic parameters (carrier density, their mobility and lifetimes) control in bulk mercury-cadmium telluride (MCT) using the nanosecond laser irradiation induced shock waves (LSW) is investigated. MCT bulk samples (with composition x=0.2) both n- and p- type with different initial structural quality were treated. The post-treatment changes have been detected by galvanomagnetic and photoelectric (lifetime) techniques. Two depending of irradiation mode mechanisms of interaction between LSW and bulk Hg 1 - X Cd X Te defect subsystem are given. The potentiality of this technique as a technological tool for controlled modification of MCT parameters is discussed.

Yury N. Nikiforov

Papers

Laser shock waves as a tool of changing the strains in materials

Laser-induced shock waves processing of II–VI solid solutions interface

Controling the properties of bulk Hg1-xCdxTe by laser-induced shock waves

On control the properties of bulk Hg1-xCdxTe by laser induced shock waves