High carrier mobility of CoPc wires based field-effect transistors using bi-layer gate dielectric

Gedda, Murali; Subbarao, Nimmakayala V. V.; Obaidulla, Sk Md; Goswami, Dipak Kumar

doi:10.1063/1.4834355

Cited by 8 publications

(3 citation statements)

References 25 publications

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“…Hence, CoPc molecules draw less attention for the fabrication of electronic devices. Recently, the significant enhancement of carrier mobility is observed on the devices based on CoPc wires where better molecular alignment was observed . The performance of CoPc thin film based devices can also be enhanced with the detailed knowledge of the film growth.…”

Section: Introductionmentioning

confidence: 99%

Local Diffusion Induced Roughening in Cobalt Phthalocyanine Thin Film Growth

Gedda¹,

Subbarao²,

Goswami

2014

Langmuir

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We have studied the kinetic roughening in the growth of cobalt phthalocyanine (CoPc) thin films grown on SiO2/Si(001) surfaces as a function of the deposition time and the growth temperature using atomic force microscopy (AFM). We have observed that the growth exhibits the formation of irregular islands, which grow laterally as well as vertically with coverage of CoPc molecules, resulting rough film formation. Our analysis further disclosed that such formation is due to an instability in the growth induced by local diffusion of the molecules following an anomalous scaling behavior. The instability relates the (ln(t))(1/2), with t as deposition time, dependence of the local surface slope as described in nonequilibrium film growth. The roughening has been characterized by calculating different scaling exponents α, β, and 1/z determined from the height fluctuations obtained from AFM images. We obtained an average roughness exponent α = 0.78 ± 0.04. The interface width (W) increases following a power law as W ∼ t(β), with growth exponent β = 0.37 ± 0.05 and lateral correlation length (ξ) grows as ξ ∼ t(1/z) with dynamic exponent 1/z = 0.23 ± 0.06. The exponents revealed that the growth belongs to a different class of universality.

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Section: Introductionmentioning

confidence: 99%

Local Diffusion Induced Roughening in Cobalt Phthalocyanine Thin Film Growth

Gedda¹,

Subbarao²,

Goswami

2014

Langmuir

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“…Bottom‐gate top‐contact OFET device geometry was used for microstructure based device fabrication. A similar dielectric system was described in previous reports ,. The device consists of an aluminum (Al) bottom gate, Al 2 O 3 /polyvinyl alcohol (PVA) bi‐layer dielectric system, organic active channel and gold (Au) source‐drain electrodes.…”

Section: Methodsmentioning

confidence: 99%

One‐Dimensional Porphyrin–Fullerene (C₆₀) Assemblies: Role of Central Metal Ion in Enhancing Ambipolar Mobility

Goudappagouda

Gedda

Babu

2018

Chemistry A European J

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One-dimensional (1D) nanostructures of π-conjugated molecules exhibiting excellent charge carrier mobilities have attracted much interest for use in organic electronic devices. Although it is tedious to form such structures, the availability of highly delocalized electron and hole carriers in these donor (D)-acceptor (A) coassemblies realize ambipolar charge transport. Here we demonstrate the use of a simple solution casting method to create an ambipolar donor-acceptor single-crystalline assembly. 1D assemblies of 5,10,15,20-tetraphenylporphyrins (H TPP, ZnTPP) and fullerene (C ) exhibit high ambipolar mobility in the range of 0.8-3.4 cm Vs for electrons and holes with high ON/OFF ratio and low threshold voltage. A direct experimental proof for the pivotal role of the central Zn in tetraphenyl porphyrin, which enables a strong D-A charge transfer interaction in the cocrystal and thereby induces electron (1.35 cm Vs ), hole (3.42 cm Vs ) mobilities, the highest reported for two component D-A assemblies using solution casting, is demonstrated.

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“…A typical design of such devices is shown in Figure a. In order to reduce the leakage current and to minimize the thickness of the subsequent polymer dielectric layers, a 10 nm thick Al 2 O 3 film was grown by converting a portion of Al film by an anodization process. − PVA ( M W = 89000–98000 g/mol), PS ( M W = 170000 g/mol), PVP ( M W = 25000 g/mol), CuPc (all Sigma-Aldrich) and PMMA ( M W = 5,50 000 g/mol) (Alfa-Aesar) were used without further purification. A set of polymer solutions were prepared by dissolving 30 mg/mL PVA in deionized water, 30 mg/mL PS in toluene, and 30 mg/mL PVP in freshly dried and distilled tetrahydrofuran (THF).…”

Section: Methodsmentioning

confidence: 99%

Enhanced Environmental Stability Induced by Effective Polarization of a Polar Dielectric Layer in a Trilayer Dielectric System of Organic Field-Effect Transistors: A Quantitative Study

Subbarao¹,

Gedda²,

Iyer³

et al. 2015

ACS Appl. Mater. Interfaces

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We report a concept fabrication method that helps to improve the performance and stability of copper phthalocyanine (CuPc) based organic field-effect transistors (OFETs) in ambient. The devices were fabricated using a trilayer dielectric system that contains a bilayer polymer dielectrics consisting of a hydrophobic thin layer of poly(methyl methacrylate) (PMMA) on poly(vinyl alcohol) (PVA) or poly(4-vinylphenol) (PVP) or polystyrene (PS) with Al2O3 as a third layer. We have explored the peculiarities in the device performance (i.e., superior performance under ambient humidity), which are caused due to the polarization of dipoles residing in the polar dielectric material. The anomalous behavior of the bias-stress measured under vacuum has been explained successfully by a stretched exponential function modified by adding a time dependent dipole polarization term. The OFET with a dielectric layer of PVA or PVP containing hydroxyl groups has shown enhanced characteristics and remains highly stable without any degradation even after 300 days in ambient with three times enhancement in carrier mobility (0.015 cm(2)·V(-1)·s(-1)) compared to vacuum. This has been attributed to the enhanced polarization of hydroxyl groups in the presence of absorbed water molecules at the CuPc/PMMA interface. In addition, a model has been proposed based on the polarization of hydroxyl groups to explain the enhanced stability in these devices. We believe that this general method using a trilayer dielectric system can be extended to fabricate other OFETs with materials that are known to show high performances under vacuum but degrade under ambient conditions.

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High carrier mobility of CoPc wires based field-effect transistors using bi-layer gate dielectric

Cited by 8 publications

References 25 publications

Local Diffusion Induced Roughening in Cobalt Phthalocyanine Thin Film Growth

Local Diffusion Induced Roughening in Cobalt Phthalocyanine Thin Film Growth

One‐Dimensional Porphyrin–Fullerene (C₆₀) Assemblies: Role of Central Metal Ion in Enhancing Ambipolar Mobility

Enhanced Environmental Stability Induced by Effective Polarization of a Polar Dielectric Layer in a Trilayer Dielectric System of Organic Field-Effect Transistors: A Quantitative Study

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High carrier mobility of CoPc wires based field-effect transistors using bi-layer gate dielectric

Cited by 8 publications

References 25 publications

Local Diffusion Induced Roughening in Cobalt Phthalocyanine Thin Film Growth

Local Diffusion Induced Roughening in Cobalt Phthalocyanine Thin Film Growth

One‐Dimensional Porphyrin–Fullerene (C60) Assemblies: Role of Central Metal Ion in Enhancing Ambipolar Mobility

Enhanced Environmental Stability Induced by Effective Polarization of a Polar Dielectric Layer in a Trilayer Dielectric System of Organic Field-Effect Transistors: A Quantitative Study

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One‐Dimensional Porphyrin–Fullerene (C₆₀) Assemblies: Role of Central Metal Ion in Enhancing Ambipolar Mobility