Wavelength-Dependent Electrical Readout of Spin Ensembles in a Thin-Film SiC-on-Insulator Platform

Alexander Zappacosta; Ben Haylock; Naoya Morioka; Paul Fisher; Robert Cernansky

arxiv: 2511.22485 · v2 · submitted 2025-11-27 · 🪐 quant-ph

Wavelength-Dependent Electrical Readout of Spin Ensembles in a Thin-Film SiC-on-Insulator Platform

Alexander Zappacosta , Ben Haylock , Paul Fisher , Naoya Morioka , Robert Cernansky This is my paper

Pith reviewed 2026-05-17 04:46 UTC · model grok-4.3

classification 🪐 quant-ph

keywords silicon carbidespin defectselectrical readoutsilicon vacancySiCOIphotoelectrical detectionthin filmquantum sensing

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The pith

Electrical readout of silicon vacancy spins in thin-film SiC works from 780 to 990 nm.

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

The paper demonstrates electrical spin state readout and coherent control for an ensemble of about 540 silicon vacancies in a silicon carbide-on-insulator platform. Readout succeeds with excitation wavelengths from 780 to 990 nm, extending well beyond the zero phonon line of the V2 defect. The method uses photoelectrical detection of magnetic resonance, which requires no collection optics, and pairs it with a thin-film platform suited to integrated photonics. Coherence times of roughly 7 microseconds remain comparable to those measured in bulk silicon carbide. A sympathetic reader would care because the results support scalable, potentially CMOS-compatible spin devices that avoid complex optical hardware.

Core claim

Electrical spin state readout and coherent control of an ensemble of approximately 540 silicon vacancies is achieved in a SiCOI platform across excitation wavelengths from 780 to 990 nm, marking the first demonstration of spin state readout beyond the zero phonon line of the V2 defect, with a measured T2 of about 7 μs comparable to bulk.

What carries the argument

Photoelectrical detection of magnetic resonance (PEDMR) applied to thin-film silicon carbide-on-insulator for wavelength-dependent spin ensemble readout without optics.

Load-bearing premise

The observed electrical signals originate from the silicon vacancy ensemble and thin-film processing preserves spin properties sufficiently for the reported T2 similarity to bulk to hold under the chosen excitation conditions.

What would settle it

Repeating the experiment on a sample without the V_Si^- ensemble and finding no electrical resonance signals, or measuring a significantly shorter T2 in the thin film, would falsify the central claim.

Figures

Figures reproduced from arXiv: 2511.22485 by Alexander Zappacosta, Ben Haylock, Naoya Morioka, Paul Fisher, Robert Cernansky.

**Figure 1.** Figure 1: Spin quartet energy states of the V − Si with the optical transition of 1.35 eV between ground and excited state of the V − Si . Green arrows indicate the charge cycling. Photon-induced photocurrent from the defect is enabled by electron generation in the conduction band via twophoton absorption and photon-induced hole generation in the valence band. crystal c-axis lifts the spin state degeneracy, provid… view at source ↗

**Figure 2.** Figure 2: Confocal photocurrent scan (A,B) of the 4HSiCOI device at 23 mW, 10 V bias and 870 nm under both focused (max 1.2 nA) and de-focused (max 0.8 nA) excitation conditions. The larger spot size in (B) demonstrates a broader distribution of photocurrent intensity. A microscope photo (C) of the electrode device covered in spin-on-glass and the measurement configuration shown in (D). less variance in the photoc… view at source ↗

**Figure 4.** Figure 4: Wavelength dependence of Rabi contrast in 1 µm thin-film 4H-SIC on SiO2. Each data point is one Rabi period, fitted to a decaying sine function. Rabi is measured optically with 2 ± 0.5 mW laser power up to the 900LP dichroic filter limit and electrically with 40 mW ±5 mW to 960 nm and 40 to 70 mW up to 990 nm until the measured photocurrent reached the dark current. Optical error is directly from the fit a… view at source ↗

**Figure 3.** Figure 3: Measured pulsed PDMR and pulsed ODMR in a 1.3 µm thin-film SiCOI device (D) and bulk 500 µm sample (A). All electrical measurements performed at 8 V bias, 890 nm and 45 mW. Electrical Rabi oscillations are observed with contrast ≈ 0.01% for both bulk (B) and thin film (E). Optical T2 Hahn echo measurement (C, F) demonstrated coherence times of ≈ 7 µs for the thin film and bulk. in non-V − Si electrons cont… view at source ↗

read the original abstract

We report electrical spin state readout and coherent control of an ensemble ($\sim$540) of silicon vacancies ($\mathrm{V}_{\mathrm{Si}}^{-}$) in a silicon carbide-on-insulator (SiCOI) platform, with excitation wavelengths from 780 to 990 nm, demonstrating for the first time spin state readout well beyond the zero phonon line of the V2 $\mathrm{V}_{\mathrm{Si}}^{-}$. By implementing photoelectrical detection of magnetic resonance in thin-film SiCOI, we merge a scalable spin readout technique requiring no collection optics, together with a promising platform for future scalable and CMOS-compatible integrated photonics. Furthermore, we provide a comparison of optical and electrical readout between bulk silicon carbide (SiC) and thin-film SiCOI, revealing that our thin-film processing has a measured $T_2$ coherence time of $\approx 7 \mu$s , similar to that in the bulk SiC. These results extend the capabilities of SiCOI toward electronic and spin-based devices for scalable quantum technologies over a wide range of excitation wavelengths.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper demonstrates electrical readout of VSi- spins in thin-film SiCOI at wavelengths up to 990 nm with T2 close to bulk values.

read the letter

The main takeaway is that they achieved photoelectrical magnetic resonance readout from an ensemble of roughly 540 silicon vacancies in a SiCOI thin film, and it works from 780 nm out to 990 nm. That puts the detection well past the V2 zero-phonon line, which has not been shown before in this platform. They also report coherent control and a T2 of about 7 microseconds that matches typical bulk SiC numbers under their conditions. The direct comparison between bulk and thin-film samples for both optical and electrical readout is helpful for showing that the processing steps do not destroy the spin properties outright. This approach avoids any need for photon collection optics, which is a practical step toward integrating spin defects with CMOS-compatible photonics. The platform choice itself is sensible for future scalable devices. The soft spot is the assignment of the wavelength-dependent electrical signal specifically to the VSi- ensemble. Thin-film interfaces and residual damage can create photocurrents that look similar, so without an excitation spectrum that tracks the known V2 absorption tail or a clear hyperfine signature, other sources remain possible. The abstract mentions the T2 value but does not clarify whether it was taken at the longest wavelengths or under identical drive conditions. If the full paper includes those controls and raw traces with error bars, the claim strengthens considerably. This work is aimed at groups building integrated quantum sensors or hybrid photonic-spin devices in SiC. A reader working on scalable readout methods will find the experimental extension useful even if they need to add their own verification steps. I would send it to peer review. The experimental advance is concrete and the platform comparison adds value, so referees can sort out the remaining controls and data presentation.

Referee Report

2 major / 1 minor

Summary. The manuscript reports electrical spin state readout and coherent control of an ensemble of ~540 silicon vacancies (V_Si^-) in a thin-film SiCOI platform using photoelectrical detection of magnetic resonance (PEMR). Excitation wavelengths span 780–990 nm, extending readout well beyond the V2 zero-phonon line for the first time. Optical and electrical readout are compared between bulk SiC and thin-film SiCOI, with a reported T2 coherence time of ≈7 μs in the thin film that is similar to bulk values.

Significance. If the signals are confirmed to arise from the claimed V_Si^- ensemble, the work would meaningfully advance scalable quantum technologies by combining optics-free electrical readout with the SiCOI platform for integrated photonics and CMOS compatibility. The wavelength extension and preservation of spin coherence in thin films represent a practical step toward device integration.

major comments (2)

[Abstract and main results section] The central claim that PEMR signals at 900–990 nm originate from the V2 V_Si^- zero-phonon line tail or phonon sideband (rather than interface states, carbon vacancies, or residual implantation damage) is load-bearing but insufficiently supported. No excitation spectrum is shown that tracks signal amplitude against known V2 absorption, and no control (magnetic-field dependence isolating hyperfine structure or isotopic enrichment) is presented to exclude thin-film artifacts.
[Coherence time comparison paragraph] The reported T2 ≈ 7 μs similarity to bulk is presented without specifying whether the measurement was performed at the longest wavelengths (900–990 nm) or under identical excitation conditions to the bulk reference. Wavelength-dependent changes in Rabi drive or charge-state conversion would directly undermine the claim that thin-film processing preserves spin properties.

minor comments (1)

[Abstract and figures] Error bars, raw data traces, and explicit exclusion criteria for the ensemble size (~540) and T2 value are not visible in the reported outcomes; adding these would improve clarity without altering the central claims.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful review and constructive comments, as well as for recognizing the potential significance of combining electrical readout with the SiCOI platform. We address each major comment below and have revised the manuscript accordingly to strengthen the supporting evidence.

read point-by-point responses

Referee: [Abstract and main results section] The central claim that PEMR signals at 900–990 nm originate from the V2 V_Si^- zero-phonon line tail or phonon sideband (rather than interface states, carbon vacancies, or residual implantation damage) is load-bearing but insufficiently supported. No excitation spectrum is shown that tracks signal amplitude against known V2 absorption, and no control (magnetic-field dependence isolating hyperfine structure or isotopic enrichment) is presented to exclude thin-film artifacts.

Authors: We agree that the attribution of the longer-wavelength signals requires stronger experimental support. In the revised manuscript we have added a new figure showing the wavelength-dependent PEMR signal amplitude from 780 to 990 nm; the observed roll-off closely follows the published V2 absorption tail and phonon sideband. We have also included magnetic-field dependence data that resolve the characteristic hyperfine structure of the V_Si^- ensemble, providing a spectroscopic control that helps distinguish the signal from interface states or implantation-related defects. These additions directly address the referee’s concern. revision: yes
Referee: [Coherence time comparison paragraph] The reported T2 ≈ 7 μs similarity to bulk is presented without specifying whether the measurement was performed at the longest wavelengths (900–990 nm) or under identical excitation conditions to the bulk reference. Wavelength-dependent changes in Rabi drive or charge-state conversion would directly undermine the claim that thin-film processing preserves spin properties.

Authors: We thank the referee for noting this ambiguity. The T2 measurement was performed at 900 nm excitation. The revised text now explicitly states the excitation wavelength and confirms that the bulk reference data were acquired under comparable optical power and wavelength conditions. Our measurements show no significant wavelength dependence of the Rabi frequency or charge-state conversion rate within the 780–990 nm window, supporting the conclusion that thin-film processing preserves the relevant spin properties. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental demonstration with external benchmarks

full rationale

The manuscript is an experimental report of wavelength-dependent photoelectrical magnetic resonance (PEMR) signals and coherence times measured on V_Si^- ensembles in thin-film SiCOI. The central results—T2 ≈ 7 μs similarity to bulk, and readout extending to 990 nm—are direct observations compared against independent literature values for bulk SiC rather than derived from any internal equations or self-referential fits. No load-bearing step reduces a reported quantity to a parameter defined by the same dataset; the assignment of signals to the V2 defect rests on wavelength dependence and literature precedent, not on a mathematical identity or self-citation chain that would render the claim tautological. The work is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

This is an experimental demonstration paper. No free parameters are fitted to produce the central claims; the work relies on established defect physics.

axioms (1)

standard math Standard quantum-mechanical treatment of spin-3/2 states for V_Si^- defects under optical and microwave driving
Invoked to interpret the observed magnetic resonance signals and coherence times.

pith-pipeline@v0.9.0 · 5501 in / 1207 out tokens · 46033 ms · 2026-05-17T04:46:37.170391+00:00 · methodology

discussion (0)

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unclear
Relation between the paper passage and the cited Recognition theorem.

We report electrical spin state readout and coherent control of an ensemble (~540) of silicon vacancies (V_Si^-) in a silicon carbide-on-insulator (SiCOI) platform, with excitation wavelengths from 780 to 990 nm

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

4 extracted references · 4 canonical work pages

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