The effect of oxygen on the electrical characteristics of triclinic lead phthalocyanine

Ahmad, A.; Collins, R. A.

doi:10.1016/0040-6090(92)90608-e

Cited by 40 publications

(7 citation statements)

References 36 publications

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“…The control experiment showed a slight but consistent increase in current for the second testing, most likely due to oxygen doping in the films, which is well documented in phthalocyanine materials, due to the slow introduction with time of partially oxidized Pcs, which act to "dope" the Pc film. [47][48][49][50] This doping acts to increase the drain currents but decrease the degree of saturation with time. Currents on the second chip, which underwent irradiation with 254-nm light to polymerize the film, consistently showed a decrease in current following the polymerization process [ Fig.…”

Section: Ofet Behavior For Films Of Pc 1 and Pcmentioning

confidence: 99%

Anisotropies in the electrical properties of rod-like aggregates of liquid crystalline phthalocyanines: Direct current conductivities and field-effect mobilities

et al. 2004

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The direct current (dc) conductivities and organic field-effect transistor (OFET) characteristics of a class of octa-substituted liquid crystalline (discotic mesophase) phthalocyanines (Pcs) are discussed. These molecules self-organize into columnar aggregates with large coherence lengths (up to approximately 300 nm). Langmuir–Blodgett films of these molecules were horizontally transferred to either interdigitated microelectrodes (IME) or OFET substrates, so that current flow could be measured either parallel or perpendicular to the column axis. Twenty-eight bilayer films of these Pcs on the IME substrates showed anisotropies in dc conductivity up to 50:1, whereas similar Pc films showed anisotropies in field effect mobilities of approximately 10:1, for a variety of W/L ratios (source/drain dimensions and spacing). Field-effect mobilities of 1 to 5 × 10-6 cm2·V-1·s-1 were determined from OFET measurements, along the Pc column axis, whereas charge mobilities measured from the space charge limited current regime on the IME substrates were in the range of 10-4 cm2·V-1·s-1. Conductive tip atomic force microscopy measurements on the apprximately 500-nm length scale showed that the conductivity anisotropy can be as high as 1000:1 when the Pc columns are intimately contacted to an adjacent Au bond pad.

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Section: Ofet Behavior For Films Of Pc 1 and Pcmentioning

confidence: 99%

Anisotropies in the electrical properties of rod-like aggregates of liquid crystalline phthalocyanines: Direct current conductivities and field-effect mobilities

et al. 2004

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“…A linear J-V characteristic at low voltages followed by nonlinear V dependences at higher voltages was claimed in many cases. [3][4][5][6][7] Generally, the current density in the linear ("Ohmic") regime was expected to be given as J = nμqV /L, although an explicit length or thickness dependence experimental study is usually lacking. Many other studies investigate only the high-voltage dependence, overlooking altogether the low-voltage regime.…”

Section: Introductionmentioning

confidence: 99%

“…[8][9][10][11][12] The temperature dependence of the current in the Ohmic regime is usually characterized using Arrhenius plots, in which the slopes of the linear regions give the activation energies for hopping transport. 5,7,13 All these studies are generally characterized by a lack of comprehensive experimental investigations in a wide parameter range, and a complete theory that can simultaneously and correctly describe the voltage, thickness, and temperature dependence of the current.…”

Section: Introductionmentioning

confidence: 99%

Exponential behavior of the Ohmic transport in organic films

et al. 2011

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An exponential dependence of conductance on thickness and temperature was found in the low-voltage, Ohmic regime of copper (CuPc) and cobalt (CoPc) phthalocyanine, sandwiched between palladium and gold electrodes unlike ever claimed in organic materials. To assure cleanliness and integrity of the electrode-phthalocyanine interface, the devices were prepared in situ, using organic molecular beam deposition with a floating shadow mask. The dc transport measurements in a wide temperature and thickness range show that (i) the low-voltage J-V curve is linear, with current increasing sharply at higher voltages, (ii) the low-voltage conductance increases exponentially with temperature, and (iii) it decreases exponentially with film thickness. A comparison with conventional models fails to explain all the data with a single set of parameters. On the other hand, a model outlined here, which incorporates tunneling between localized states with thermally induced overlap, agrees with the data and decouples the contributions to conductance from the electrode-film interface and the bulk of the film.

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“…Most of the phthalocyanines are p-type due to an absorbed Oxygen which acts as an acceptor level in band gap [9]. The oxygen impurities, which are unavoidably introduced in the preparation of organic semiconductors [10] appear to play the dual role of both acceptors and traps levels [11]. However, these impurities, as well as voids and defects which give rise to extrinsic conductivity [12] can be removed by heat treatment.…”

Section: Introductionmentioning

confidence: 99%

Structural and electrical properties of thermally evaporated cobalt phthalocyanine (CoPc) thin films

Soliman

El-Barry

Khosifan

et al. 2006

Eur. Phys. J. Appl. Phys.

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Thin films of CoPc of various thickness have been deposited onto glass substrates using thermal evaporation technique at room temperature. The dark electrical resistivity measurements were carried out at different temperature range (298-423 K). An estimation of mean free path (0) of charge carriers in CoPc thin films and bulk resistivity, ρB was attempted. Measurements of thermoelectric power confirm that CoPc thin films behave as p-type semiconductors. The ac conductivity (σac) has been investigated in the frequency range (10 2-10 6 Hz) and temperature range (298-407 K). σac is found to be proportional to ω s where s ≈ 0.879 which is frequency and temperature independence. The ac conductivity interpreted by the correlated barrier hopping (CBH) model with centers of intimate valence alternation pairs type with a maximum barrier height, WM ≈ 1.594 eV.

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The effect of oxygen on the electrical characteristics of triclinic lead phthalocyanine

Cited by 40 publications

References 36 publications

Anisotropies in the electrical properties of rod-like aggregates of liquid crystalline phthalocyanines: Direct current conductivities and field-effect mobilities

Anisotropies in the electrical properties of rod-like aggregates of liquid crystalline phthalocyanines: Direct current conductivities and field-effect mobilities

Exponential behavior of the Ohmic transport in organic films

Structural and electrical properties of thermally evaporated cobalt phthalocyanine (CoPc) thin films

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