• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.966-969
• /
• 2003

Thin film capacitors with Al-Polymer-Al sandwich structure were fabricated. The bottom and top aluminium (Al) electrodes were deposited by vacuum evaporation and copper phthalocyanine (CuPc), polyaniline-emeraldine base (Pani-EB) and cobalt phthalocyanine/polyaniline - emeraldine base (CoPc /Pani-EB) blend films (which can be used as buffer hole injection layer in OLEDs) were deposited by spin coating technique. X-ray diffractograms indicated amorphous nature of the polymer films whose thicknesses were measured by capacitance and Rutherford Backscattering Spectrometry (RBS) methods. AC conduction studies revealed that the conduction mechanism responsible in these films is variable range hopping of polarons. From D.C conduction studies, it is observed that, the nature of conduction is ohmic in the lower fields and at higher fields the dominating D.C conduction is of Poole-Frenkel type.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.1
• /
• pp.97-101
• /
• 2009

A new approach was applied to examine the charge generation and transport in organic photoconductive devices by Monte‐Carlo simulation utilizing multiple site interactions of carriers with all other charges within Coulomb radius. Stepwise generation frame was considered first by a charge separation process that was counted in two separate transactions, i.e., hopping against physical decay and dissociation against recombination. Thereafter, diffusion/ drifting process of free carriers was counted to follow. This method enables to examine readily the photocurrent generated alongside the charge generation efficiency. The field and temperature dependences of the efficiency and photocurrent were obtained comparable to Onsager’s and experimental data.

• Journal of the Korean Vacuum Society
• /
• v.20 no.1
• /
• pp.57-62
• /
• 2011

We have studied the electrical and magnetic transport properties of tunneling device with FePt magnetic quantum dots. The FePt nanoparticles with a diameter of 8~15 nm were embedded in a $SiO_2$ layer through thermal annealing process at temperature of $800^{\circ}C$ in $N_2$ gas ambient. The electrical properties of the tunneling device were characterized by current-voltage (I-V) measurements under the perpendicular magnetic fields at various temperatures. The nonlinear I-V curves appeared at 20 K, and then it was explained as a conductance blockade by the electron hopping model and tunneling effect through the quantum dots. It was measured also that the negative magneto-resistance ratio increased about 26.2% as increasing external magnetic field up to 9,000 G without regard for an applied electric voltage.

• Korean Journal of Materials Research
• /
• v.5 no.1
• /
• pp.3-11
• /
• 1995

$(TiO_{2})$ thin films were deposited on p-Si(100) substrate by APMOCVD using titanium isopropoxide as a source material. The deposition mechanism was well explained by the simple boundary layer theory and the apparent activation energy of the chemical reaction controlled process was 18.2kcal /mol. The asdeposited films were polycrystalline anatase phase and were transformed into rutile phase after postannealing. The postannealing time and the film thikness as well as the postannealing temperature also affected the phase transition. The C-V plot exhibited typical charateristics of MOS diode, from which the dielectric constant of about 80 was obtained. The capacitance of the annealed film was decreased but those of the Nb or Sr doped films were not changed. I-V characteristics revealed that the conduction mechanism was hopping conduction. The postannealing and the doping of Nb or Sr cause to decrease the leakage current and to increase the breakdown voltage.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.5A
• /
• pp.611-617
• /
• 2000

Asynchronous mode W-CDMA system is kmown to be quite appropriate to the next generation mobile communication system, especially in a non-homogenious cellular architecture. In this case, however, each base station needs to use different spreading code for identification, so it is a demeanding task for a mobile terminal to find the best cell site and get an accurate code synchronization at the beginning of a communication. Since slow acquisition of a base station could mean the failure of initiation, a fast algorithm to accelerate the cell search process is essential. In this paper, a new cell search algorithm based on the binary code position modulation within the code block is proposed. Different cell sites are identified by different hopping code sequences, andeach position modulation is performed by the hopping code. The proposed algorithm is proved to make the cell search time in most places in a cell much shorter than the previous algorithms, and to make the receiver implementation simpler.

• Journal of the Korean Magnetic Resonance Society
• /
• v.7 no.2
• /
• pp.74-79
• /
• 2003

Li[Ni,Mn,Co]O$_2$ electrode has been studied by $\^$7/Li MAS NMR. A sharp resonance at -1 ppm and a very broad resonance at approximately 400 ppm are assigned to the Li ions in Co-only environment and Ni/Mn(Co) environment, respectively, indicating a segragation of Co ions and Ni/Mn ions. Different temperature behavior of the peak position is observed for Co-only environment and Ni/Mn(Co) environment. Oxidation of Ni ions is involved during the entire charging process. At high temperature, a peak narrowing caused by the electron hopping is observed.

• Proceedings of the Korea Multimedia Society Conference
• /
• 2012.05a
• /
• pp.89-92
• /
• 2012

Wireless Mesh Network expanded the capability of the conventional wireless networking by allowing the nodes to operate in proactive mode, reactive mode or the combination of both, the hybrid mode in the multi-hopping nature. By doing so, the links between the nodes become much more robust and reliable because of the number of paths to reach a destination node from a source node can be more than 1 and do not need to rely on the access point (AP) alone to relay the messages. As there may be many possible ways to form an end-to-end link between 2 nodes, the routing security becomes another main concern of the 802.11s protocol. Besides its reliance on the 802.11i for the security measures, 802.11s also includes some new features such as the Mesh Temporal Key (MTK) and the Simultaneous Authentication of Equals (SAE). The authentication and key management (AKM) process of 802.11s were observed in this paper.

• Electrical & Electronic Materials
• /
• v.9 no.8
• /
• pp.776-782
• /
• 1996

The electrical properties of vapor deposition polymerized polymide thin films for getting an in-line system with manufacturing process of semiconductor device, have been studied. Polyimide thin films fabricated by vapor deposition polymerization(VDP) method based on PMDA and 4,4'-DDE monomer were confirmed by FT-IR spectra. It is found that the major conduction carriers of thin films are ions, and the hopping length of ions is almost same with monomer length at the temperature over 120.deg. C through the analysis of electrical conduction mechanism. Also, The activation energy is about 0.69 eV at the temperature of >$30^{\circ}C$ - >$150^{\circ}C$ and it is shown that the resistivity at which thin films can be used as an insulating film between layers of semiconductor device, is 3.2*10$^{15}$ .ohm.cm.

• Electrical & Electronic Materials
• /
• v.10 no.6
• /
• pp.581-588
• /
• 1997

The ionization energy and degree of ionization for Si and Ge with boron doping are calculated. The hole mobilities are then calculated as a function of doping concentration using the relaxation time approximation. When the screening effect is taken into account, the reduction of ionization energy results in the increase of degree of ionization. As a result, the calculated Si mobility becomes closer to the experimental data, whereas the calculated Ge mobility is almost independent of the screening effect. The inclusion of the broadening effect in the mobility calculation overestimates the ionized impurity scattering. As compared with the experiment, the screening effect is not avoidable to calculate Si and Ge mobilities, and the broadening effect must accompany with the hopping process.

• Journal of the Korean Ceramic Society
• /
• v.35 no.8
• /
• pp.885-889
• /
• 1998

The temperature dependence of dc conductivity and magnetic properties of cation deficient {{{{ { {(LaMn) }_{1-λ }O }_{3 } }} systems has been investigated,. Above 160K the magnetic susceptibility of all samples followed the Curie-Weiss law. The Curie temperature decreased as the cation deficiency increased. This is due to a strong Jahn-Teller effect originated from electrons of {{{{ { Mn}^{3+ } }} In the case of samples annealed in air and oxygen at-mosphere the charge carriers responsible for conduction in the ferromagnetic regime below the Curie tem-perature are believed to have both magnetic and lattice characteristics. However the conduction carriers in the paramagnetic regime above the Curie temperature are though to be formed by hopping process of small polarons which were generated by assistance of the Jahn-Teller effect.