Capacitance/voltage measurements

Schematic energy level diagrams of a metal/polymer/metal structure before and after the layers are in contact are shown in the top two drawings of Figure 11-6. Before contact, the metals and the polymer have relative energies determined by the metal work functions and the electron affinity and ionization potential of the polymer. After contact there is a built-in electric field in the structure due to the different Schottky energy barriers of the asymmetric metal contacts. Capacitance-voltage measurements demonstrate that the metal/polymer/metal structures are fully depleted and therefore the electric field is constant throughout the bulk of the structure [31, 35]. The built-in potential, Vhh i.e. the product of the constant built-in electric field and the layer thickness may be written...

Parker [55] studied the IN properties of MEH-PPV sandwiched between various low-and high work-function materials. He proposed a model for such photodiodes, where the charge carriers are transported in a rigid band model. Electrons and holes can tunnel into or leave the polymer when the applied field tilts the polymer bands so that the tunnel barriers can be overcome. It must be noted that a rigid band model is only appropriate for very low intrinsic carrier concentrations in MEH-PPV. Capacitance-voltage measurements for these devices indicated an upper limit for the dark carrier concentration of 1014 cm"3. Further measurements of the built in fields of MEH-PPV sandwiched between metal electrodes are in agreement with the results found by Parker. Electro absorption measurements [56, 57] showed that various metals did not introduce interface states in the single-particle gap of the polymer that pins the Schottky contact. Of course this does not imply that the metal and the polymer do not interact [58, 59] but these interactions do not pin the Schottky barrier. 

Y. Huang, X.D. Chen, S. Fung, C.D. Beling and C.C. Ling, Spatial characterization of a 2 inch GaN wafer by Raman spectroscopy and capacitance-voltage measurements, J. Phys. D Appl. Phys., 37, 2814-2818 (2004). 

S. Chandra and J. Singh, Capacitance-voltage measurement technique as a tool for in situ characterization of electrochemical etching of silicon, J. Electrochem. Soc. 146, 1206, 1999. 

Huang, Y. and Williams, C.C., Capacitance-voltage measurement and modeling on a nanometer-scale by scanning C-V microscopy, J. Vac. Sci. TechnoL, B 12, 369-372, 1994. 

Photoluminescence (PL) and EL spectroscopy can be used to determine the presence of traps. Other techniques include current voltage measurements, capacitance voltage measurements, capacitance transient spectroscopy, and admittance spectroscopy. Under favorite conditions, the identification of the nature of the trap is possible. 

Light-induced changes in the electrostatics at the semiconductor-electrolyte interface are conveniently probed by capacitance-voltage measurements in the dark and under illumination of the semiconductor electrode. If charge trapping at the interface plays a decisive role (whatever be the mechanism), the voltage... 

Horowitz, G. Capacitance voltage measurements and flat-band potential determination on Zr-doped alpha-Fe203 single-crystal electrodes. J. Electroanal. Chem. 159, 421 (1983)... 

The migration of atomic Si in 5-doped samples was studied by means of capacitance-voltage measurements and rapid thermal annealing. It was shown that these methods could detect diffusion which occurred at length-scales as small as Inm. The capacitance-voltage profile widths broadened, from less than 4nm to 13.7nm, upon annealing (lOOOC, 5s). It was found that the results could be described by ... 

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