Electrical conductivity determination of semiconductors by utilizing photography, finite element simulation and resistance measurement

A new method is developed to measure precisely and reliably the electrical conductivity of a block-shaped semiconductor specimen using four-wire technique with electrodes in arbitrary shape and position. No effort for accurate electrode preparation is necessary anymore. This method may be especially applied to measure the conductivity of ceramics at high temperatures, when typical spring-contacts or clamp-contacts are not possible and instead wound wires are used for electrically contacting the specimen. The method comprises the following: An image of the specimen is processed to a 3D model. By applying a finite element simulation on this 3D model, a form factor (also called geometry factor) that considers the effect of the non-infinitesimally small electrodes is calculated. Together with the measured resistance (preferably in four-wire technique), the actual conductivity of the sample is derived. Experimental results confirmed the validity of the proposed method. As a limitation of the method, the conductivity of the specimen should be within the range of 0.01 Sm−1 and 106 Sm−1.

SmartTilt: The Sensible Way of Tilting

Tilting a crystalline material in the Transmission Electron Microscope to bring it to a particular crystallographic orientation can be an experience that varies from the almost trivial (e.g. in the case of a large single-crystal piece of silicon in a semiconductor specimen) to something that frustrates even the most experienced operator (e.g. in the case of nanometre-sized crystals in a polycrystalline matrix). The problems encountered during such tilting experiments have to do mostly with the following characteristics of the double-tilt holder and goniometer of the microscope:•the second tilt is not eucentric•the mechanical characteristics of the goniometer and specimen holder are such that the forces applied by the tilt drive mechanism can lead to displacements ranging from a few to hundreds of nanometres•the tilt required commonly involves a combination of α and β tilts.Normally the operator has to juggle to keep the crystal within the beam (by applying corrections to the x and/or z goniometer axes), set or adjust the tilt speeds for the α and β tilts, judge how much to tilt with α and β, and assess the result on the diffraction pattern. As a consequence, the whole procedure is normally done in increments, with many intermediate steps, corrections for overshoots, and so on. The time taken to tilt a particular crystal is inversely related to its size. For an experienced operator who knows the relative orientations of the diffraction pattern and the tilt direction, tilting a very small crystal sometimes can take up to tens of minutes. For an inexperienced operator, the procedure commonly results in losing track of the crystal and having to start over with another one.

Tertiary Interferograms in Fourier Transform Spectroscopy

Multiple passes, both within a semiconductor specimen and between the specimen surface and the interferometer, give rise to a series of extraneous “tertiary” interferograms in a Fourier transform spectrophotometer. These tertiary interferograms can lead to a possible error on the order of 1% in the measurement of the impurity content of a silicon wafer. However, this effect can be eliminated by a straightforward manipulation of the interferogram prior to transformation.