2.?Sensor PreparationThe Hall sensor structure preparation method has been described in detail in previous papers [14,15]. Hence, here we give only a brief description of the method. The sensitive element of the sensors is an n-InSb www.selleckchem.com/products/AP24534.html thin film, about 1 ��m thick, epitaxially grown on a GaAs (100) substrate by the flash-evaporation epitaxy method. During the film growth, donor doping with tin is performed. As a result, the electron concentration in the film is (2�C3) �� 1018 cm?3. This concentration is optimum for preparing a HS with a very good thermal stability of the main parameters over a wide range of temperatures. The thickness of 1 ��m is also chosen to optimize the sensor parameters.The electron mobility in InSb thin films decreases with the film thickness below 3 ��m, and particularly strongly below 1 ��m [16].

Hence, the advantage from the Hall voltage increase resulting from the film thickness decrease is largely reduced or lost because Inhibitors,Modulators,Libraries of the increase in sensor resistance. Moreover, thinner InSb films, Inhibitors,Modulators,Libraries about 1 ��m in thickness, have a very weakly temperature dependent resistance [14] in a broad temperature range, which allows biasing the 1 ��m HS also in the constant voltage regime [17].In order to protect the sensitive InSb thin-film structure from the hot ambient, it is covered with a protective layer. For that purpose, a 0.1 ��m SiOx (x �� 2) layer deposited in vacuum is used. After Inhibitors,Modulators,Libraries the InSb films deposition, the films are photolitographically cross-shaped and equipped with 0.5 ��m Cr/Au electrodes by vacuum evaporation.

Finally, the GaAs chip is divided onto 3 �� 3 mm2 sensor structures. The resulting HS structure is shown in Figure 1(a).Figure 1.Extreme-temperature Inhibitors,Modulators,Libraries Hall sensor; (a) ETHS structure. Maltese cross-shaped InSb layer is plated with Cr-Au electrodes, and (b) ETHS in an open ET package.The HS structure is mounted in a HT package, as shown in Figure 1(b). The package is based on a 12 �� 6-mm2 base plate made of Al2O3 or AlN. The base plate has four electric traces formed by silk-screen printing of thick AgPt films. The Hall structure is attached to the base plate with HT Al2O3 paste (PELCO High Performance Ceramic Adhesive, www.tedpella.com). In the next step the electric connections to the conducting paths are formed. The contacts to the gold electrodes of the InSb film are made by a standard thermocompression bonding with a 100-��m diameter gold wire.

The gold wire and the electrode are then covered with HT silver paste (AMEPOX, Electon 40AC Anacetrapib paste, www.amepox-mc.com), therefore, the connection is formed of HT Tofacitinib Citrate cost silver paste with a gold core. Such a contact has very good mechanical and electric properties in a wide temperature range. On the other end of the base plate, the contacts between the external wires and the four electric traces are formed by HT silver paste covered with HT Al2O3 paste for mechanical strengthening.