981,447. Electron microscopes; electrostatic holding devices. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Aug. 26, 1963 [Aug. 29, 1962], No. 33693/63. Headings H1D and H1P. An electron microscope is provided with an object stage in the form of a heat apertured disc 6 within an opening in which the object 8 is arranged and by means of which the object is movable in any lateral direction, together with at least one body 19 of semi-conductor material connected to the object stage 6 and arranged to contact a stationary part 11 of the microscope, the arrangement being such that, when a voltage is set up between the stationary part 11 and a conductive layer 22 on that surface of the body 19 remote from the part 11, electrostatic forces between the body 19 and the part 11 clamp the object stage 6 in such a manner as to prevent axial movement thereof. Suitable semi-conductor materials are slate, marble, agate and certain ceramic synthetic materials having a resistivity of approximately 1010 ohm-cm. In the embodiment shown an annular block 19 of agate provided with a vapour-deposited layer 22 of silver is rigidly connected in an annular groove 20 of the disc 6 with the interposition of a coating 21 of insulating material. A battery 27 and switch 28 are connected between the conductive layer 22 and the stationary part 11 by way of a lead 23 and the wall 13 of the microscope housing. Specification 824,903 is referred to.

Disclosed is a method of measuring thickness or a surface profile of a thin film layer formed on a base layer through a white light scanning interferometry, the method including: preparing simulation interference signals corresponding to thicknesses by assuming a plurality of sample thin film layers different in thickness from one another and simulating interference signals with respect to the respective sample thin film layers; acquiring a real interference signal with respect to an optical-axis direction of entering the thin film layer by illuminating the thin film layer with white light; preparing a plurality of estimated thicknesses that the thin film layer may have on the basis of the real interference signal; comparing whether the simulation interference signal having thickness corresponding to the estimated thickness is substantially matched with the real interference signal; and determining the thickness of the simulation interference signal substantially matched with the real interference signal as the thickness of the thin film layer.

Semi-conductor devices are described which consists of a disc of N-type germanium containing three grain boundaries radiating symmetrically from the centre of the disc (and thus including 120 degrees angles). Germanium tricrystals for use in such devices can be prepared by crystalline growths from three single barshaped seeds of square cross-section. A 30 degrees relative misorientation is introduced between each pair of seeds by relative rotation of the seeds about the growth direction. The tricrystal is then grown by either a horizontal zone melting method or by the Czochralski method. A tricrystal thus prepared may be used as a seed for future growths. U.S.A. Specification 2,740,901 is referred to.

1,005,343. Wave guide switches. ALBISWERK ZURICH A.G. Feb. 15, 1963 [Feb. 16, 1962], No. 6153/63. Heading H1W. [Also in Division H4] A single antenna is coupled to both a transmitter and a receiver via impedance transforming networks which contain semi-conductor diodes acting to give the desired high or low impedance. In Fig. 1 the lines A, S, E lead to the antenna, transmitter and receiver respectively. The impedance transforming network across the transmitter comprises lines 9, 10, which are of a length (2n+ 1)#/4 equal to an odd number of quarter wavelengths of the transmitting frequency connected at their ends by diodes 11, 12 inanti-parallel. The line 8 between this network and line A is also of length (2n+ 1)#/4, similarly the network leading to the receiver comprises lines 2, 3 of length (2n+ 1)#/4 and diodes 5, 6. When the trans- mitter S produces an R.F. pulse the diodes 5, 6, 11, 12 conduct in the appropriate half cycles presenting low resistance at the ends of the lines. This means that the input impedance of the branches are high and little energy is lost. On receipt of a pulse by the antenna the diodes are non-conductive because the lower energy of the received pulse is below their threshold voltage. The diodes therefore present high resistance at the end of the lines. The input impedance for lines 2, 3 is low while that for lines 8, 9, 10 is high and so the received energy passes to the receiver. Single diodes in each branch may be adequate in some cases. In order to receive higher signal energies the diodes may be back biased during reception and forward biased during transmission. An alternative embodiment is shown in Figs. 2A and 2B in which oscillatory circuits with zero impedance at the transmitter frequency are used. In the receiver line coupling (2A) the diodes 21 are so connected that they short circuit the input of the receiver for transmitted signals but open the input for reception. In the transmitter line coupling (2B), however, the diodes 25 and 28 provide a signal path during transmission but break the path during reception.

978,143. Electric meters; electric bridge circuits; liquid level measuring apparatus; indicating apparatus. BENDIX CORPORATION. March 14, 1963 [March 26, 1962], No. 10212/63. Headings G1J, G1N, G1Q and G1U. [Also in Divisions G4 and H3] The output voltage of a capacitive liquid level measuring bridge uses a circuit comprising a number of transistors of opposite conductivity type are arranged in cascade such that as the D.C. input signal rises the output voltage first rises and then falls. Fig. 1 comprises two such cascades in succession so that the final output voltage rises and falls twice. It is explained mathematically that so long as the signal voltage is below the level at which the respective output transistors 59 and 72 saturate the gain of each circuits is 2 but when they saturate the output voltage (e.g. E2) is related to the input voltage (e.g. E 1 ) by the relation E 2 = V - 2E 1 where V is the supply voltage. The circuit is used to measure the voltage from a liquid level indicator Fig. 3. The liquid level measuring capacitance 81 is connected in a capacitive bridge fed with alternating current from source 84 and having its output amplified at 85 rectified at 86 and 90 and then applied across a potential variable capacitor 83 in the form of a semi-conductor diode so as to balance the bridge, isolating chokes being provided to separate the A.C. path from the D.C. path. Rectified output from the amplifier is fed to a first meter 93 calibrated in metres and through a folding circuit similar to Fig. 1 to a meter 95 calibrated in decimetres. As the level of the liquid rises from 0 to 1 metre the pointer of meter 93 moves clockwise from 0 to 1 and the pointer of 95 moves in clockwise direction from 0 to 10. A further rise of 1 to 2 metres increases the reading on 93 from 1 to 2 but, as the output of the folding-circuit is now falling, causes the pointer of meter 95 to rotate in an anticlockwise direction towards its initial position, readings being taken from the inner scale. Further rise from 2 to 3 metres causes the pointer of metre 95 to move clockwise again while the rise from 3 to 4 metres causes pointer of metre 95 to return in an anticlockwise direction.

1,188,933. Dosimeter. SCIENCE RESEARCH COUNCIL. 22 Nov., 1967 [22 Aug., 1966], No. 37438/66. Heading H5R. A dosimeter comprises a container having a substantially constant volume under the conditions of measurement employed, a solid material within the container, which material when irradiated by the radiation to be measured, evolves a gas in a quantity related to the radiation dose and means to indicate the pressure within the container. The material exemplified is polyethylene in the form of a powder or as a thin film, e.g. 0À003 inch in thickness, the film being inserted in the container as a roll. The pressure indicating means may be a Bourdon gauge communicating with the interior of the chamber, or the container may be closed and the pressure be indicated by a strain gauge associated with the wall of the container. As a variant on this alternative, one wall of the chamber may be constituted by a diaphragm and movement of this diaphragm may be used to indicate the pressure in the container.

1,008,473. Measuring temperature electrically. May 29, 1964 [May 30,1963], No. 21747/63, Heading G1N. The junction temperature of a semi-conductor device 10 is measured by adding two signals V 1 and V 2 , one of which, V 1 , represents the temperature of an external part of the device 10 as measured by a thermistor 12 mounted on the same heat sink 11 as the device, and the other of which, V 2 , is derived in a circuit, 9, from the output of a current transformer 16 whose primary 17 carries the current which flows through the junction. The signal V 2 is said to be proportional to the temperature difference between the outer parts of the device and its junction. The circuit 9, which represents an electrical analogue of the thermal circuit of the device, contains capacitors 21 to effectively short circuit any transients in the junction current, which would not affect the junction temperature because of the thermal inertia of the device and therefore are required not to produce any effect upon the signal V2. The voltage V3 may be compared with a reference voltage and used to operate a protection relay if it exceeds a predetermined value.

686,948. Semi-conductor amplifiers. STANDARD TELEPHONES & CABLES, Ltd. March 2, 1951, No. 5113/51. Drawings to Specification. Class 40 (iv). A crystal triode comprises a body of semiconductor material containing a donor impurity, a first thin layer containing an acceptor material on one of its surfaces, and a second thin layer containing donor material on the first layer, and a base electrode, and two rectifying electrodes respectively contacting the first and second layers. Alternatively, the specified donor and acceptor characteristics may be interchanged throughout. The Specification refers to an electro-forming process for a crystal triode and the use of donor or acceptor material on the collector electrode as described in Specification 681,809, which improves the current gain characteristics of the device. Improvement in current-gain may also be obtained by adding donor or acceptor material to the surface layer of the semi-conductor of N- or P-type respectively, and this may be derived from a collector electrode containing such material by carrying out the above electro-forming process, or by overloading such a collector electrode during normal use. After surface treatment, collector electrodes without such added material may be used, and may consist of pure tungsten, or an electrode plated as described in Specification 686,915. Phosphorus, antimony and arsenic are given as examples of donor material and may be deposited on a tungsten wire forming the electrode. The emitter electrode may also consist of phosphor-bronze material.