Polished Plane Research Articles

Upside-down fabricated GaP monolithic display

An upside-down fabricated GaP monolithic display having p-n junctions formed by zinc diffusion is developed and the feasibility of practical use studied. In this device, the zinc diffusion is performed at a temperature in the vicinity of 650 °C to increase the efficiency. The device front plane with the p-n-junction segments faces the substrate upon which individual digits are assembled, and the light emitted from the p-n junctions travels through the GaP chip and exits from the polished back plane, which faces the observer. The individual wire bonding of each segment is eliminated using flip-chip technique. It is thought that this device is the most suitable for practical use.

Prebreakdown currents in ultrahigh-vacuum gaps between aluminium electrodes

Measurements of prebreakdown currents have been made for highly polished plane parallel aluminium electrodes in an ultrahigh vacuum (10−9 torr), as a function of electrode separation, in the range 0.076–2.8 mm. The prebreakdown currents are found to be consistent with the Fowler-Nordheim field-emission theory. The field-in tensification factor is calculated at each gap separation. For gap separations larger than 0.89 mm, a large increase in the prebreakdown current, at a particular applied voltage (ignition), is observed. The ratio of the current increase, depending on electrode separation, is observed to be in the range 10–160. The ignition voltage is determined as a function of gap separation and found to increase with increasing gap separation. It is suggested that the ignition can only occur at a given gap separation, when the prerequisite values of a prebreakdown current, combined with an applied voltage, are simultaneously present. At short gap separations (≪0.76 mm), the ignition phenomenon is absent. It is shown that this is because the condition for the required current value cannot be satisfied at the required ignition voltage.

The splitting strength of mica

Two well-ground and polished plane glass plates if put together, adhere. This phenomenon is called optical contact and is very much used in the manu­facture of optical instruments, since the boundary between the two glass surfaces shows practically no reflection of light, when the gap between the two glass surfaces is exceedingly small in comparison with the wave-length of visible light. An analogous phenomenon can be easily observed in mica. Two freshly split mica foils if put together adhere again with an appreciable force. It is interesting to see if the restoration is perfect, i. e ., if we need to apply the same force to split two mica sheets placed in optical contact as to split a fresh one. In the present work it will be shown that the splitting strength is a constant for mica ; that we can determine a surface energy of mica which is independent of the shape of the mica sheets chosen and that mica placed in optical contact is totally restored. A description will also be given of some electrical phenomena obtained by splitting mica in a high vacuum. It appears that the cleavage surface of mica is covered with electrical charges ; further, that the strength of mica in a high vacuum is more than in air and is also a fairly well-defined constant. The present observations are connected with the well-known work of A. Joffé on the tensile strength of rock salt. In the case of rock salt the surface was either dissolved to avoid the effect of imperfections of the surface or the surface action was avoided altogether as in the experiment with the rock salt sphere.