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Langer, D.

Publications and source records attributed to Langer, D..

A reactive system for open terrain navigation: Performance and limitations

We describe a core system for autonomous navigation in outdoor natural terrain. The system consists of three parts: a perception module which processes range images to identify untraversable regions of the terrain, a local map management module which maintains a representation of the environment in the vicinity of the vehicle, and a planning module which issues commands to the vehicle controller. Our approach is to use the concept of 'early traversability evaluation', and on the use of reactive planning for generating commands to drive the vehicle. We argue that our approach leads to a robust and efficient navigation system. We illustrate our approach by an experiment in which a vehicle travelled autonomously for one kilometer through unmapped cross-country terrain.

Langer, D.↗

Ellipsometric study of silicon nitride on gallium arsenide

A method for optimizing the sensitivity of ellipsometric measurements for thin dielectric films on semiconductors is described in simple physical terms. The technique is demonstrated for the case of sputtered silicon nitride films on gallium arsenide.

Alterovitz, S. A.↗

Ellipsometric studies of sputtered silicon nitride on n-GaAs

Ellipsometry, which is the study of optical systems through their effect on polarized light, is a nondestructive technique offering extremely high sensitivity and in situ operation. One of the intriguing possibilities is to make use of the high sensitivity of ellipsometry for studying the very thin interface between an insulating film and a semiconductor substrate. Researchers have been especially interested in native or anodic oxides. In a recent study, Aspnes and Theeten used ellipsometry to study the interface between silicon and its thermally grown oxide, SiO2. These authors were able to conclude that the interface consisted of a 7 +/- 2 A graded region of atomically mixed silicon and oxygen. In this paper we report both analysis and experimental results for the system: sputtered silicon nitride on (100) n-type gallium arsenide.

Peng, Y. K.↗