Zinc oxide (ZnO) is a promising wide-bandgap semiconductor due to its favorable properties for a variety of demanding device applications such as UV light emitters/detectors, high-power and high-temperature devices. The presence of defects in the material can considerably change the electrical properties of the semiconductors. However, recently it has been found that the terminated face of the material significantly alter the characteristics of such devices. The defects in ZnO have been studied in last decades, but no clear consensus has been made. This dissertation investigates the electrical properties of defects in ZnO grown by hydrothermal and molecular beam epitaxy techniques using deep level transient spectroscopy (DLTS). Among the growth techniques available to grow the thin film, the hydrothermal is one of the most cheap and user friendly technique. DLTS provides a sensitive method for identifying defects and for determining their parameters. The main findings are as follow: A. Several circular Schottky contacts (1mm diameter) with Pd metal on the Znface and O-face on n-type ZnO grown by hydrothermal and Ohmic contact of nickel-gold on the backside were deposited by e-beam technique. The asobtained samples were labeled as group A and B samples, respectively. The present literature on n-type ZnO has highlighted a defect, labeled as E3 irrespective of growth technique, which is also studied thoroughly in this research project. The respective summary of each group A and B of samples is explained below: · DLTS has been carried out on the group A samples to study deep level defects. Its result showed two electron trap level E1 having activation energy Ec-0.22 ±0.02 eV and E2 with activation energy Ec-0.49 ±0.05 3 eV. E1 level has time-delayed transformation of shallow donor defects zincinterstitial and vacancyoxygen (Zni-VO) complex. It is observed through X-ray differaction that the preferred direction of ZnO growth is along (10 1 0) plane i.e. VO-Zni complex, assuming that under favourable condition (Zni-VO) complex is transformed into a zinc antisite (ZnO). Consequently, the trap concentration increases with decreasing free carrier concentration. Hence, the ZnO is correlated to E1 level demonstrating the increase in concentration. · Several renowned research groups have revealed different points defects in bulk ZnO like naming oxygen vacancy, zinc interstitial, and/or zinc antisite. These defects having activation energy (free carrier concentration) in the range of 0.32–0.22 eV (1014 -1017 cm-3 ) below conduction band. The results of group A and B samples also showed activation energy (free carrier concentration) as observed by other renowned research groups. This result is due to activation energy of the level while it is not conceivable by with Vincent et al.,[ J. Appl. Phys. 50 (1979) 5484]. They believed that data should be carefully interpreted obtaining by capacitance transient measurement of diodes having carrier concentration greater than 1015 cm -3 . Thus the influence of background free-carrier concentration, ND induced field on the emission rate signatures of an electron point defect in ZnO Schottky devices has been studied by using deep level transient spectroscopy. Many theoretical models were tested on the experimental data to understand the mechanism. Our findings were supported by PooleFrenkel model based on Coulomb potential. It is revealed by 4 investigation that Zn related charged impurities were found to be responsible for electron trap. Results were also tested through qualitative measurements like current-voltage and capacitance-voltage measurements. B. Several Schottky contacts of 1mm diameter with silver were prepared on ZnO grown by molecular beam epitaxy. These samples were labeled as group C samples, DLTS measurements revealed a hole trap exhibiting metastability effect in the emission rates of trap with storage time. We determined that hole trap transfers from one configuration to other with storage time. As a result the activation energy of the acceptor level varied in the range of 0.31 eV to 0.49 eV above the valance band at different measurement time. Impurities cannot be removed in the growth procedure. SIMS results showed the presence of nitrogen. During the growth process nitrogen occupies O site and produces Zn-N complex. But Zn-N bond is not stable because of its large bonding energy and consequently results into metastable nature of the defect. All experimental findings and available literature support the conclusion that the observed hole trap arise from Zn-N complex. C. The ZnO nanorods were grown on glass substrate coated with different metal (Ni, Al, Ag and Au) by aqueous chemical growth. These samples were labeled as D, E, F and G, respectively. The structural properties of ZnO nanorods were investigated by X-Ray diffraction (XRD) and scanning electron microscopy (SEM). The intensity of ZnO (0 0 2) diffraction peak in X-ray diffraction pattern is maximum of sample D because of nucleation of Ni metal coated on substrate. SEM measurements strongly support our observation that thin layer Ni metal increases the growth of nanorods.
دلبر تے رکھ آس زیادہ دیکھنی پئے گی یاس زیادہ کملا کردا گلاں فر فر ’’دانا کرے قیاس زیادہ‘‘ وچ لڑائیاں فائدے نالوں ہوندی ستیا ناس زیادہ مایوسی چھڈ رحمت رب تے رکھے بندہ آس زیادہ عاشق تسّے دید تری دے ودھ گئی ڈھیر پیاس زیادہ ڈردے لوک برائلر کولوں شہدا سمجھن ماس زیادہ صحبت بریاں لوکاں والی مینوں نہیں ہے راس زیادہ
Islam has given a complete code of life to run the system of this universe, which started with the arrival of Hazrat Adam (A.S) in this world and was completed with the Prophet (P.B.U.H). It is a comprehensive and system in which the individual and the rights and duties of both congregations are based on the concept of justice and fairness. Under this system of Islam, the supreme command on earth is only Allah’s persons, the position of man is that of vicegerent and caliph, mans responsibility is to carry out all the affairs of life according to the will of Allah. The earth and its resources will created for the benefits of all mankind. All human beings have the right to use them according to their needs, but no individual has the right to seize or hoard these resources to the detriment of others. Just as every person has rights, such as protection of life and property, honor and reputation, so it is also his duty to provide comfort and relief to no other people and not to cause any harm to anyone.
Compression of data has become a worldwide phenomenon during the past few decades for reason of achieving savings in band-width (BW) and hence makes it cost effective. The widespread practice of encryption of data has generated interest for many decades and it mainly aims at protection of data. Combining these two apparently contrary processes (in terms of BW) is quite challenging. Whereas the research on concurrent data compression and data protection (encryption) is still on, the methodology adopted by the author is unique and quite new. The most important aim of data compression technique is the need for curtailing the data storage and communication expenses. The source message (long) is converted to a codeword (small). The key objective of data encryption is to guard the integrity of data if it is intercepted by an eavesdropper. The plaintext is transformed in to ciphertext using an encryption key or keys. Combining the processes of compression and encryption together must be done in this order, that is, compression followed by encryption because all compression techniques heavily rely on the redundancies inherently part of a regular text or speech. The speech compression has been achieved using Lempel-Ziv 78 algorithm and a new algorithm for encryption/decryption, named ―The RandomOne, abbreviated as TR-1‖ is developed during this study and is thoroughly tested. The results obtained are quite encouraging. Firstly, contrary to the use of conventional methods the algorithm developed in this study does not use exclusive-OR (XOR) operation in Permutation (P) and Distribution (D) boxes for producing ciphertext from the plaintext. In this scheme pseudo random number (PRN) is used only to deceive the intruder by adding more confusion (meaning compared to the confusion due to the use of some tested algorithms used in this research). In fact only the sender of information and the intended recipient (not intruders) should be aware of the 44 bit positions filled by the PRN in a 128 word. The intended recipient discards these during deciphering process at the right time (these are disposed of before performing the inverse mapping in the P-Box). Secondly, protection against attacks is further ensured by using two supplementary keys, one for the P-Box, and another for the D-box. In addition the routine key-set of the N selected algorithms further enhances the security. In a small set-up, the distribution of key-set can be mutually agreed upon by the users; but in a large set-up, the distribution of these sets can be accomplished using standard key distribution techniques. Moreover, the proposed algorithm also differs from the other methods currently in use due to deployment of a ―sentinel marker”; which is not adopted by other algorithms and this proposal is purely the brain child of the author. The sentinel marker is part of the secret key which is pre-decided and predetermined by the sender and the intended recipient of the information. Twenty bits (out of a total of 128) are used for the sentinel marker which amounts to 2^20 = 1,048,576 possibilities combined with 2^44 = 17.6 trillion possibilities of the ciphertext produced by the PRN. The job for the cryptanalyst to break this cipher becomes formidable and a fool-proof security of data is ensured.