Nano-scale resistivity reduction in single-grain of lead phthalocyanine

Tabuchi, Sho; Otsuka, Yoichi; Kanai, Masaki; Tabata, Hitoshi; Matsumoto, Takuya; Kawai, Tomoji

doi:10.1016/j.orgel.2010.02.011

Cited by 6 publications

(4 citation statements)

References 29 publications

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“…This technique has been used to investigate the local electrical properties of carbon nanotubes [13][14][15] and organic nanowires on insulators. 16,17) The method can also be used for the local conduction measurements of organic thin films, 18) however, the local field-effect characteristics of organic thin films have never been carried out by PCI-AFM to the authors' knowledge. Since the performance of the OFETs are strongly influenced by their operating environments, it is also important to perform PCI-AFM in various gaseous environments including a vacuum.…”

Section: Introductionmentioning

confidence: 99%

Investigations of Local Electrical Characteristics of a Pentacene Thin Film by Point-Contact Current Imaging Atomic Force Microscopy

Kimura

Miyato

Kobayashi

et al. 2012

Jpn. J. Appl. Phys.

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We performed local electrical property measurements on a pentacene semiconducting thin film, which was connected to a Pt electrode, using point-contact current imaging atomic force microscopy (PCI-AFM). The measurements were conducted not only under ambient conditions, but also in a vacuum on the same film by employing the Q-control method to reduce the settling time of the cantilever oscillation amplitude. In both environments, the obtained current images showed that the current in the film gradually decreased with the increasing distance from the electrode. We also found differences in the threshold voltage among the grains and discontinuities in the apparent resistance at the grain boundaries, which suggest that the conductance of the thin film is limited by the grain boundaries. Moreover, by comparison of the measurement results on the same grains in air and in a vacuum, an increase in the current and a shift in the threshold voltage to a positive value in air were observed, which can be attributed to the exposure of the film to atmospheric oxygen.

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Section: Introductionmentioning

confidence: 99%

Investigations of Local Electrical Characteristics of a Pentacene Thin Film by Point-Contact Current Imaging Atomic Force Microscopy

Kimura

Miyato

Kobayashi

et al. 2012

Jpn. J. Appl. Phys.

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“…The vastly different optoelectronic characteristics of the monoclinic and triclinic PbPc polymorph make controlling the PbPc film structure crucial for optimizing device operation. Phase transitions have been achieved by templating using different substrates and substrate treatments, postdeposition annealing, , applying pressure, or changing deposition conditions. , The obtained control over PbPc film structure has been applied for optimization of switches, thin film transistors and gas sensors, , but was never exploited for solar cell applications. The use of PbPc as a donor material in organic solar cells deposited on top of a ZnPc templating layer has been reported, giving an optimized PCE of 1.95% .…”

Section: Introductionmentioning

confidence: 99%

Structural Evolution of Evaporated Lead Phthalocyanine Thin Films for Near-Infrared Sensitive Solar Cells

et al. 2010

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In this work, we focus on the deposition conditions as a means to control the structural evolution of lead phthalocyanine (PbPc) films in order to promote the triclinic structure, thereby inducing a shift in the absorption spectrum toward the near-infrared (NIR). Absorption spectra of PbPc films exhibit an enhanced NIR absorption peak at a wavelength of λ = 900 nm upon (i) increasing film thickness, (ii) increasing substrate temperature, or (iii) decreasing evaporation rate. X-ray diffraction measurements correlate the enhancement of the NIR absorption peak with an improved crystallinity and increased average volume of triclinic domains in the mixed monoclinic−triclinic films. As the surface structure of 10 and 60 nm thick films differ, this implies an asymmetric layer structure with a semicrystalline monoclinic film close to the substrate, evolving to a predominantly triclinic structure in the upper part of the film. We have demonstrated the use of structural control of the PbPc layer in a planar heterojunction solar cell with NIR-sensitivity. Decreasing the evaporation rate results in solar cells with significantly enhanced short-circuit current density (J SC), because of the change in absorption in combination with the longer exciton diffusion length that was estimated for donor layers exhibiting a predominantly triclinic structure. Overall, an optimized solar cell yields a power conversion efficiency of 2.6% (2.1% when correcting for the solar spectrum mismatch), and has external quantum efficiencies above 11% from λ = 320−990 nm with a peak value of 34% at λ = 900 nm.

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“…Spin relaxation in the Cu layer is negligible since the Cu layer (10–20 nm) is thinner than the spin diffusion length of Cu (∼400 nm at room temperature) . Also, we can ignore the spin injection into molecule layer because of the exceedingly large resistivity of PbPc and H 2 Pc (∼100 Ωm) , compared with metals. The typical FMR spectra and the induced S–C conversion signals in NiFe/Cu(10 nm)/PbPc(1 molecular layer (ML)), NiFe/PbPc, and NiFe/Cu(10 nm)/H 2 Pc(1 ML) multilayer structures are shown in Figure e.…”

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confidence: 99%

Realization of Spin-dependent Functionality by Covering a Metal Surface with a Single Layer of Molecules

et al. 2019

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An interface of molecule and metal has attracted much attention in the research field of nanoelectronics because of their high degree of design freedom. Here, we demonstrate an efficient spin-to-charge current conversion at the metal surface covered by a single layer of molecules. Spin currents are injected into an interface between metal (Cu) and lead(II) phthalocyanine by means of the spin pumping method. An observed voltage signal is caused by the inverse Edelstein effect, i.e., spin-to-charge current conversion at the interface. The conversion coefficient, inverse Edelstein length, is estimated to be 0.40 ± 0.06 nm, comparable with the largest Rashba spin splitting of interfaces with heavy metals. Interestingly, the Edelstein length strongly depends on the thickness of the molecule and takes a maximum value when a single layer of molecules is formed on the Cu surface. Comparative analysis between scanning probe microscopy and first-principles calculations reveal that the formation of interface state with Rashba spin splitting causes the inverse Edelstein effect, whose magnitude is sensitive to the adsorption configuration of the molecules.

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Nano-scale resistivity reduction in single-grain of lead phthalocyanine

Cited by 6 publications

References 29 publications

Investigations of Local Electrical Characteristics of a Pentacene Thin Film by Point-Contact Current Imaging Atomic Force Microscopy

Investigations of Local Electrical Characteristics of a Pentacene Thin Film by Point-Contact Current Imaging Atomic Force Microscopy

Structural Evolution of Evaporated Lead Phthalocyanine Thin Films for Near-Infrared Sensitive Solar Cells

Realization of Spin-dependent Functionality by Covering a Metal Surface with a Single Layer of Molecules

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