Andrew Lang (physicist)

Andrew Lang was a 20th-century physicist primarily known for his contributions to X-ray topography, a technique used to image crystal defects. His work significantly advanced the field of materials science by providing a non-destructive method for characterizing the internal structure of crystals with high resolution.

Lang developed what is now known as the Lang method of X-ray topography, which involves scanning a narrow X-ray beam across a crystal and recording the diffracted X-ray intensity on a photographic plate. This technique allowed for the direct visualization of dislocations, stacking faults, and other imperfections within the crystal lattice. The resulting images, called topographs, provide valuable information about the density, distribution, and nature of these defects.

Lang's early work focused on developing the experimental apparatus and theoretical understanding necessary for implementing X-ray topography. He established the optimal conditions for achieving high resolution and contrast in topographs, and he developed methods for interpreting the images to extract quantitative information about crystal defects.

His research had a significant impact on the study of semiconductors, metals, and other crystalline materials. X-ray topography, as pioneered by Lang, became an essential tool for characterizing crystal quality and understanding the relationship between crystal defects and material properties. This understanding is crucial for optimizing the performance of electronic devices, improving the strength of structural materials, and advancing our fundamental knowledge of solid-state physics.

Beyond his work on X-ray topography, Lang also contributed to the development of other X-ray diffraction techniques. He published numerous papers on his research, and his work continues to be cited by scientists and engineers working in materials science and related fields.