Persistent photocurrent characteristics of ZnO polycrystalline films prepared by RF magnetron sputtering

Worasawat, Suchada; Tasaki, Katsuyosi; Neo, Yoichiro; Pecharapa, Wisanu; Hatanaka, Y.; Mimura, Hidenori

doi:10.7567/1347-4065/ab0d0f

Cited by 3 publications

(12 citation statements)

References 36 publications

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“…3(b) the recovery of the photocurrent accelerates with the increasing light-intensity, which is consistent with the observations of most previous works. [7,11,12,14,15] Time dependence of photocurrent rise and decay can be generally described by the stretch-exponential model. [22] Photocurrent rise follows…”

Section: Ppc Effect In E-mode A-igzo Tftsmentioning

confidence: 99%

“…In previous works on PPC effect, the dependence of the PPC recovery activation energy on light-intensity was studied in Ref. [12], the activation energy for the photo-excitation was rarely observed. In Ref.…”

Section: Ppc Effect In E-mode A-igzo Tftsmentioning

confidence: 99%

“…Kim et al observed that PPC recovery slowed down with increasing the light-intensity in a-IGZO TFTs, [10] while Lu et al observed the opposite dependency in ZnO films. [7,11,12] In other semiconductor materials, [13][14][15] Singh et al observed that PPC recovery slowed down with increasing the light-intensity in Se-Ge-In related materials, [13] while Polyakov et al reported an opposite dependency in AlGaN [14] and GaN. [15] It is noted that there are no reasonable explanations for these contradictory observations, and a systematic study is needed.…”

Section: Introductionmentioning

confidence: 99%

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A systematic study of light dependency of persistent photoconductivity in a-InGaZnO thin-film transistors*

Wang

Zhang

et al. 2020

Chinese Phys. B

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Persistent photoconductivity (PPC) effect and its light-intensity dependence of both enhancement and depletion (E-/D-) mode amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) are systematically investigated. Density of oxygen vacancy (VO) defects of E-mode TFTs is relatively small, in which formation of the photo-induced metastable defects is thermally activated, and the activation energy (E a) decreases continuously with increasing light-intensity. Density of VO defects of D-mode TFTs is much larger, in which the formation of photo-induced metastable defects is found to be spontaneous instead of thermally activated. Furthermore, for the first time it is found that a threshold dose of light-exposure is required to form fully developed photo-induced metastable defects. Under low light-exposure below the threshold, only a low PPC barrier is formed and the PPC recovery is fast. With increasing the light-exposure to the threshold, the lattice relaxation of metal cations adjacent to the doubly ionized oxygen vacancies ( V O 2 + ) is fully developed, and the PPC barrier increases to ∼ 0.25 eV, which remains basically unchanged under higher light-exposure. Based on the density of VO defects in the channel and the condition of light illumination, a unified model of formation of photo-induced metastable defects in a-IGZO TFTs is proposed to explain the experimental observations.

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Section: Ppc Effect In E-mode A-igzo Tftsmentioning

confidence: 99%

Section: Ppc Effect In E-mode A-igzo Tftsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A systematic study of light dependency of persistent photoconductivity in a-InGaZnO thin-film transistors*

Wang

Zhang

et al. 2020

Chinese Phys. B

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“…For polycrystalline materials with the grain boundaries and amorphous materials, many reports have been presented as the conduction current phenomena in the inhomogeneous media. [4][5][6][7][8] The photoconductive characteristics of wide bandgap materials strongly depend on the imperfect defect states and reveal a long decay tail after light illumination was removed the so-called persistent photocurrent (PPC), which has been well known for the past decade. 4,9,10) The interface or surface properties strongly influence the conduction current due to the influence caused by the trapping/de-trapping carriers.…”

Section: Introductionmentioning

confidence: 99%

“…14) Our previous work was on the PPC flowing laterally in ZnO polycrystalline films in argon gas atmosphere, analyzing the recombination processes in the bulk of film by using an inhomogeneous media model. 7) Recently, the PPC in ZnO nanostructures have been considerably investigated by many research groups for UV device applications and fundamental studies. [15][16][17][18][19] In addition, the surface interaction phenomena with the ambient molecules also have been intensively investigated for ZnO nanocrystalline materials.…”

Section: Introductionmentioning

confidence: 99%

Influence of oxygen assisted recombination on persistent photocurrent characteristics of ZnO polycrystalline thin films prepared by RF magnetron sputtering

Worasawat

Neo

Hatanaka

et al. 2020

Jpn. J. Appl. Phys.

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Decay characteristics in persistent photocurrent (PPC) of zinc oxide (ZnO) polycrystalline films highly aligned in the hexagonal c-axis direction (0002) deposited by radio frequency magnetron sputtering were investigated. Long-term decay of the photocurrent after turning off UV light illumination has been known as a PPC, which affected the performance of optical and electrical devices. Compared to the case of argon ambient, the decay characteristics were strongly influenced by the oxygen ambient. Our phenomenological model proposed could derive the recombination coefficient from an average waiting time that electrons/holes encounter the oxygen molecules attacking the surface of the ZnO polycrystalline films. The decay time response resulted is explained as a modified hyperbolics with the time constant τ and dispersion parameter β. Our experimental results are adapted to the theoretical equation. Using the average β value, τ dependence on the oxygen volume rate is in agreement with the theoretical one and presented a dispersive process on the surface reaction of oxygen gas. These investigations are useful for applications such as photoconductive sensors, gas sensors and a photocatalytic electrode.

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The effects of sub-bandgap transitions and the defect density of states on the photocurrent response of a single ZnO-coated silica nanospring

et al. 2020

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The electrical and optoelectronic properties of nanometer-sized ZnO structures are highly influenced by its native point defects. Understanding and controlling these defects are essential for the development of high-performance ZnO-based devices. Here, an electrical device consisting of a polycrystalline ZnO-coated silica nanospring was fabricated and used to characterize the electrical and photoconductive properties of the ZnO layer using near-UV (405 nm) and sub-bandgap (532 and 633 nm) excitation sources. We observe a photocurrent response with all three wavelengths and notably with 532 nm green illumination, which is the energy associated with deep oxygen vacancies. The polycrystalline ZnO-coated silica nanospring exhibits a high responsivity of 1740 A W−1 with the 405 nm excitation source. Physical models are presented to describe the photocurrent rise and decay behavior of each excitation source where we suggest that the rise and decay characteristics are highly dependent on the energy of the excitation source and the trapping of electrons and holes in intermediate defect levels in the bandgap. The energy levels of the trap depths were determined from the photoconductive decay data and are matched to the reported energy levels of singly and doubly ionized oxygen vacancies. A phenomenological model to describe the dependence of the saturation photocurrent on excitation intensity is presented in order to understand the characteristics of the observed breaks in the slopes of the saturation photocurrent versus excitation intensity profile.

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Persistent photocurrent characteristics of ZnO polycrystalline films prepared by RF magnetron sputtering

Cited by 3 publications

References 36 publications

A systematic study of light dependency of persistent photoconductivity in a-InGaZnO thin-film transistors*

A systematic study of light dependency of persistent photoconductivity in a-InGaZnO thin-film transistors*

Influence of oxygen assisted recombination on persistent photocurrent characteristics of ZnO polycrystalline thin films prepared by RF magnetron sputtering

The effects of sub-bandgap transitions and the defect density of states on the photocurrent response of a single ZnO-coated silica nanospring

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