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REVIEW 2 major objections 2 minor 22 references

Mitigating the photocurrent persistence of single ZnO nanowires for low noise photodetection applications

T0 review · 2 major / 2 minor · reviewed 2026-05-24 · grok-4.3

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Pith's one-line read A gate voltage sequence restores ZnO nanowire photodetectors to low dark current by reversing photocurrent persistence.

desk verdict The paper reports a two-step photocurrent rise in ZnO nanowires and a gate voltage reset method to cut persistence, but the reset's repeatability and noise impact lack supporting cycle data. read the letter →

arxiv 1907.11393 v1 pith:DMEKWBNT submitted 2019-07-26 physics.optics physics.app-ph

J.ph Girard , L. Giraudet , S Kostcheev , B Bercu , T J Puchtler , R A Taylor , C Couteau This is my paper
classification physics.opticsphysics.app-ph
keywords ZnOnanowiresphotodetectorsphotocurrentpersistenceoxygenchemisorptiongatevoltagephotoconductivegainsurfaceeffectslownoisedetection
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

ZnO nanowire photodetectors exhibit very high photoconductive gain because oxygen molecules bind to the nanowire surface. The same binding causes photocurrent to persist for hours after light exposure ends, preventing repeated measurements at useful speeds. Transient current measurements in oxygen, air, vacuum and argon at different temperatures confirm the surface origin of both effects and identify a two-step photocurrent rise that had not been reported before. From this mechanism the authors construct a gate voltage sequence that releases the adsorbed oxygen and returns the device to its starting low-dark-current condition. The method therefore removes the main practical obstacle to using these detectors in applications that require cycling.

What carries the argument

Gate voltage sequence that reverses surface oxygen chemisorption to eliminate photocurrent persistence.

What would settle it

After the gate voltage sequence is applied, the dark current fails to return to its original low value or the photocurrent persistence reappears in the next illumination cycle.

Watch

Extended reading notes

Core claim

Single ZnO nanowire photodetectors reach a photoconductive gain of 7.8 × 10^7 through oxygen chemisorption on the surface; the same process produces photocurrent that can last several hours. Current transients measured in different atmospheres and temperatures establish the surface mechanism and reveal a previously unseen two-step rise in photocurrent. Knowledge of these response steps allows an applied gate voltage sequence to reverse the chemisorption, restoring the device to its initial state with very low dark current.

Load-bearing premise

The photocurrent persistence arises from reversible oxygen chemisorption that the gate voltage sequence can fully undo without adding noise or damaging the device.

Editorial extensions

If this is right

  • The detector can be reset in seconds rather than waiting hours for natural decay.
  • The high gain of 7.8 × 10^7 becomes available for repeated measurements without long recovery intervals.
  • Low dark current is maintained after each reset, preserving low-noise operation.
  • The approach moves single-nanowire ZnO photodetectors closer to commercial use in integrated optics.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Voltage-reset protocols of this kind may apply to other surface-dominated nanowire photodetectors.
  • The two-step transient could be exploited to separate fast initial response from the slower persistent component.
  • Embedding the reset sequence in a feedback circuit might allow continuous low-noise operation in an array.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

2 major / 2 minor

Summary. The paper reports experimental measurements of photocurrent transients in single ZnO nanowire photodetectors with ohmic contacts under varying atmospheres (oxygen, air, vacuum, argon) and temperatures. It attributes high photoconductive gain (maximum G = 7.8 × 10^7) and photocurrent persistence (up to hours) to reversible surface oxygen chemisorption, notes a previously unreported two-step rise transient, and proposes a gate-voltage sequence to reset the device to its initial low-dark-current state.

Significance. If the proposed reset sequence is shown to be repeatable without added noise or degradation, the work would be significant for advancing ZnO nanowire photodetectors toward practical low-noise applications by directly addressing the persistence limitation through a mechanism-based electrical protocol.

major comments (2)
  1. [Abstract] Abstract: The reported maximum gain of 7.8 × 10^7 and the claim that the gate-voltage sequence restores the initial state with very low dark current are presented without error bars, number of devices tested, or any cycle-to-cycle statistics; these omissions directly affect the load-bearing claim that the method advances the devices toward commercial use.
  2. [Abstract and discussion of reset method] The manuscript states that the reset is established 'from a knowledge of the photocurrent response mechanisms' but supplies no quantitative post-reset metrics (noise spectral density, dark-current stability over multiple cycles, or long-term repeatability under the tested atmospheres and temperatures) to confirm that oxygen chemisorption is fully reversed without introducing instability.
minor comments (2)
  1. [Abstract] The abstract claims the two-step photocurrent rise is reported 'for the first time' without citing prior literature on ZnO nanowire transients for context.
  2. [Abstract] No mention is made of how many nanowires or devices were measured to support the atmosphere- and temperature-dependent trends.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful review and constructive feedback on our manuscript. We address the major comments point by point below and outline the revisions we will make to strengthen the presentation of our results.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The reported maximum gain of 7.8 × 10^7 and the claim that the gate-voltage sequence restores the initial state with very low dark current are presented without error bars, number of devices tested, or any cycle-to-cycle statistics; these omissions directly affect the load-bearing claim that the method advances the devices toward commercial use.

    Authors: We agree that the abstract would benefit from additional statistical context. In the revised manuscript we will report that the maximum gain value was obtained from measurements on multiple nanowires (typically 5–8 devices per atmosphere/temperature condition) and will include representative error bars derived from repeated measurements on the same device. Cycle-to-cycle statistics for the gate-voltage reset sequence will be added as a new panel or supplementary figure showing dark-current return values over at least five consecutive cycles. revision: yes

  2. Referee: [Abstract and discussion of reset method] The manuscript states that the reset is established 'from a knowledge of the photocurrent response mechanisms' but supplies no quantitative post-reset metrics (noise spectral density, dark-current stability over multiple cycles, or long-term repeatability under the tested atmospheres and temperatures) to confirm that oxygen chemisorption is fully reversed without introducing instability.

    Authors: The reset protocol was designed directly from the oxygen-chemisorption mechanism established by the atmosphere- and temperature-dependent transients. We acknowledge that the current manuscript does not provide post-reset noise spectral density or multi-cycle repeatability data. In revision we will add these quantitative metrics: noise spectral density measured before and after reset, dark-current stability over ≥10 cycles, and repeatability under oxygen, air, vacuum and argon at the temperatures already studied in the work. revision: yes

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity; purely experimental observations and method proposal

full rationale

The manuscript reports transient current measurements in varied atmospheres and temperatures, identifies oxygen chemisorption as the cause of photoconductive gain and persistence, and describes an empirical gate-voltage reset sequence. No equations, derivations, fitted parameters, or predictions appear that reduce to inputs by construction. No self-citation chains or uniqueness theorems are invoked to justify any result. The central claim rests on direct experimental data rather than any self-referential reduction.

Assumptions & free parameters 0 free parameters · 1 assumptions · 0 invented entities

The central claims rest on standard domain knowledge of ZnO surface chemistry and device physics rather than new postulates or fitted parameters.

assumptions (1)
  • domain assumption Oxygen chemisorption on the nanowire surface is responsible for the high photoconductive gain and the observed photocurrent persistence.
    Invoked to explain results from measurements in oxygen, air, vacuum, and argon atmospheres.

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Cite this review

Pith. "Pith review of Mitigating the photocurrent persistence of single ZnO nanowires for low noise photodetection applications." pith.science (2026). https://pith.science/paper/DMEKWBNT

@misc{pith2026190711393,
  author       = {Pith},
  title        = {Pith review of: Mitigating the photocurrent persistence of single ZnO nanowires for low noise photodetection applications},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/DMEKWBNT}},
  note         = {Machine review of arXiv:1907.11393}
}
abstract

In this work, we investigate the optoelectronic properties of zinc oxide (ZnO) nanowires, which are good candidates for applications based on integrated optics. Single ZnO nanowire photodetectors were fabricated with ohmic contacts. By taking current transient measurements in different atmospheres (oxygen, air, vacuum and argon), and at various temperatures, we point out the importance of surface effects on the electrical behaviour. Results confirm that oxygen chemisorption is responsible for the existence of a high photoconductive gain in these devices, and for the first time a two step process in the photocurrent rise transient is reported. A maximum gain of $G=7.8 \times 10^{7}$ is achieved. However, under certain conditions, the persistence of the photocurrent can last up to several hours and as such may prevent the device from operating at useful rates. From a knowledge of the photocurrent response mechanisms, we establish a method to restore the photodetector to its initial state, with very low dark current, by applying an appropriate gate voltage sequence. This advances the state of the art for these detectors towards commercial applications.

Figures

Figures reproduced from arXiv: 1907.11393 by the authors.

Figure 1
Figure 1. a. SEM image of a single nanowire photodetector. Scale bar is 5 µm. b. Schematic of the device, the drain-source bias Vds is applied using the Ti/Au electrodes. A gate voltage Vg is applied below the sample, by polarising the silicon substrate. polarity of the gate voltage, which facilitates the transit of charges to the electrodes and stems the persistence of the photocurrent. 2 Experimental details Our ZnO nanowir… view at source ↗
Figure 2
Figure 2. Room temperature (dark) Id − Vg transfer characteristic obtained at Vds = 1V. The measurements are performed in 1 bar oxygen atmosphere. The flow of electrons through the nanowire can be modulated by the gate voltage. Inset: Id − Vds curves for -20, 0 and 20 V gate voltage showing an almost ohmic behaviour. the Id − Vds characteristic over a range of gate voltages Vg = [−20, 20] V (see inset [PITH_FULL_IMAGE:figure… view at source ↗
Figure 3
Figure 3. a. Photoluminescence spectra of ZnO nanowires under vacuum and ambient air, at room temperature for an incident optical power of 1.5 × 106 W.m−2 b. Nanowire photoluminescence intensity variation versus excitation optical power density, in air and in vacuum. The fits are carried out with equation IPL = aPb exc + c. ear effects bypass the classical band to band recombinations and can imply bound-excitons, biexcitons, … view at source ↗
Figures from the paper (6 more)
Figure 4
Figure 4. Figure 4: a. Nanowire photocurrent response under a pure oxygen atmosphere at 5 mbar, 50 mbar and 750 mbar (respectively blue, red and orange lines). Illumination at λ = 365 nm starts at t=0 s and stops at t=300 s.b. Same curve on a log scale. c. and e. Raw data for rise and fal…
Figure 5
Figure 5. Figure 5: Schematic of the influence of oxygen on the electrical properties of the nanowire. [PITH_FULL_IMAGE:figures/full_fig_p005_5.png]
Figure 6
Figure 6. Figure 6: a. Photocurrent versus time under different atmospheres at room temperature. Illumination at 365 nm starts at t = 0 s and stops at t = 300 s. The photocurrent persistence is much longer under vacuum and argon than in presence of oxygen. b. Values obtained from the fits…
Figure 7
Figure 7. Figure 7: a. Photocurrent measurements at different temperatures (100 K-293 K), in oxygen atmosphere (0.5 mbar), illuminated at 365 nm. First photocurrent rise plateau is indicated. b. Data for rise transient on a log scale. c. First photocurrent plateau versus 1000/T: activatio…
Figure 8
Figure 8. Figure 8: a. Maximum photocurrent at 293 K in 1bar O2 atmosphere, as a function of light excitation power density for three different nanowires. b. Nanowire photodetector gain as a function of the excitation power density for the three nanowires [PITH_FULL_IMAGE:figures/full_fi…
Figure 9
Figure 9. Figure 9: Nanowire response to illumination at 365 nm in an oxygen atmosphere and at room temperature (note the log scale). Return to the initial off-state is accelerated using an appropriate gate pulse. of the nanowire to its neutral state: after illumination, the surface is fr…

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