{"id":"bae3ee25-2430-4a65-a706-a62a8a4be4f0","arxiv_id":"2608.09283","paper_version":1,"verdict":"CONDITIONAL","confidence":"LOW","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Direct density-of-states mapping shows transport-active band-tail states in oxide TFTs are exponentially suppressed with channel length, indicating size-dependent disorder-induced localization.","lead":"Using a lock-in-based electric-field penetration technique, the authors map the density of states in operating oxide-semiconductor transistors and find an exponential, channel-length-dependent suppression of band-tail states, a signature of disorder-induced electron localization. This gives a new device-level probe for disorder-dominated transport, a regime that becomes relevant as transistors scale toward low-dimensional channels.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The central Eq. 5 relies on an untested chemical-potential alignment: setting mu=0 at V_BG=0 for all channel lengths can produce an apparent exponential DOS suppression from a linear-in-L flat-band shift and an Urbach tail, with no localization needed.","rationale":"The reader's weakest assumption is also the most load-bearing in my read. The entire quantitative case for localization-length-limited DOS rests on comparing D_eff at fixed mu across devices, and the mu scale is fixed by an untested 'common reference' assumption. My analysis shows this is not merely a calibration detail: a linear-in-L flat-band offset combined with the standard exponential Urbach tail produces Eq. 5 identically, so the headline claim could be an artifact of energy-axis misalignment plus the very Vth shift the paper seeks to explain. This is a logical hole, not a violation of consensus. I find no internal inconsistency in the eFPT derivation, and the extraction of C_q from I_TG/I_TG0 follows established practice; the temperature-dependent DOS could suffer from the same alignment issue, but the extended states being unchanged is at least qualitatively consistent with a common reference. The paper does provide some independent support: the conductance-scaling localization length in Fig. S4 is in the same order of magnitude, but the text gives no numerical comparisons or error bars, and the extraction depends on the same devices and assumptions. Because the concern is addressable with additional measurements or a re-analysis, CONDITIONAL is the right verdict; the reader's low confidence is appropriate. I would not recommend REJECT because the data may well be correct, and I would not recommend ACCEPT until the alignment is validated. Hence UNCHANGED relative to the reader's verdict.","tokens_in":10771,"tokens_out":7703,"duration_ms":81615,"concrete_test":"Re-derive the mu axis for each device using an independent energy reference rather than V_BG=0: record the back-gate voltage at which I_TG/I_TG0 departs from the depletion plateau (V_dep) for every device, and align mu=0 at V_dep (or at the extrapolated flat-band from C-V). Then recompute Fig. 3d. If the exponential suppression of D_eff with L disappears or its slope changes by more than the fit uncertainty, the Eq. 5 claim is an artifact of the alignment. As a second check, intentionally shift each device's mu axis by the measured V_dep difference and verify the collapse of all D_eff(E) curves onto a single material DOS; failure to collapse disproves the common-reference assumption. Also report N devices per L and raw fit residuals.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's central claim (Eq. 5, D_eff(E,L)=D0(E)exp[-L/xi(E)]) is established by comparing the effective DOS of different-length devices at fixed chemical potential. The chemical potential for each device is computed from Eq. 4, which determines mu only up to an additive constant, and the constant is set by the stated assumption 'the chemical potential for different channel sizes is referenced to zero gate bias, assuming a common intrinsic chemical-potential reference for devices fabricated from the same film' (Sec. 'Geometric- and Temperature-Dependent Effective DOS'). This assumption is load-bearing and untested. If the flat-band or depletion-onset voltage varies with L—because of lateral film nonuniformity, doping gradients, or process-induced fixed charge—then the same nominal mu=0 corresponds to different physical energies in different devices. In that case, plotting D_eff at fixed nominal E samples the intrinsic DOS at energy E - delta_i(L). If the intrinsic tail is exponential (Urbach tail, standard in amorphous oxides) and delta_i happens to be linear in L, the resulting D_eff(L) is exactly an exponential in L with an apparent localization length even in the complete absence of localization. Moreover, the Vth shifts with L that the paper attributes to localization are themselves correlated with the alignment offset, so the interpretation risks circularity. No independent energy reference (e.g., measured depletion-onset edge, C-V flat-band, or thickness/doping calibration) is reported, and Fig. 3d presents linear fits without error bars or per-L device counts, so the exponential form is not distinguished from a shifted-tail artifact.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports a lock-in-based electric-field penetration technique (eFPT) to map the effective density of states (DOS) in dual-gate InOx and IGZO thin-film transistors. The authors claim that the extracted effective DOS follows D_eff(E,L) = D0(E) exp[-L/xi(E)] (Eq. 5), which they interpret as size-dependent band-tail localization. They further argue that this localization explains a threshold-voltage roll-off mechanism, and they show temperature dependence and process/composition trends (thickness, O2 annealing, In concentration) that they interpret as systematic suppression of disorder. The central quantitative finding is the exponential channel-length dependence of the effective DOS at fixed chemical potential.","tokens_in":11089,"tokens_out":3986,"duration_ms":42761,"significance":"If the exponential length dependence of the effective DOS were established, it would be a notable contribution: it would show that transport-active band-tail states are not a material constant but depend on device geometry, with implications for scaling of amorphous oxide transistors. The eFPT technique itself, resolving four distinct electronic regimes (deep traps, shallow tail, disorder-dominated tail, extended states), is a useful experimental advance. The paper also provides a plausible engineering narrative (reducing localization by thickness, annealing, and Ga/Zn doping). However, the central quantitative claim rests on an untested chemical-potential alignment assumption and on fits without reported statistics; the supporting conductance-scaling cross-check is performed on the same devices and does not remove the risk of artifact. The idea is significant but the evidence as presented is not yet convincing.","major_comments":[{"comment":"The chemical-potential alignment assumption is load-bearing and untested. The text states: 'The chemical potential for different channel sizes is referenced to zero gate bias, assuming a common intrinsic chemical-potential reference for devices fabricated from the same film.' If the flat-band or depletion-onset voltage varies with channel length (due to lateral film nonuniformity, doping gradients, or process-induced fixed charge), then the same nominal mu corresponds to different physical energies in different devices. For an intrinsic exponential Urbach tail, a linear-in-L offset in the energy reference produces an apparent D_eff(L) = D0 exp(-L/xi) with no localization at all. The manuscript does not provide an independent energy reference (e.g., depletion-onset edge, C-V flat-band, or thickness/doping calibration) for the different devices. Without such a check, Eq. (5) is not established; the authors should either validate the common-reference assumption experimentally or re-analyze the data at fixed back-gate voltage and demonstrate that the exponential suppression persists.","section":"Geometric- and Temperature-Dependent Effective DOS, Eq. (5)"},{"comment":"The fits that support the exponential decay do not include error bars, confidence intervals, or goodness-of-fit statistics. The data in Fig. 3d appear to consist of five channel lengths (10–50 um) with no indication of device-to-device spread or measurement uncertainty. The extracted xi(E) values in Fig. S3 are therefore not accompanied by any uncertainty estimate. Given that the entire localization claim rests on the slopes of these lines, the authors should provide per-energy-point standard deviations, fit residuals, and the sensitivity of xi(E) to the choice of energy alignment and to the inclusion/exclusion of individual devices.","section":"Figure 3d and Figure S3"},{"comment":"The 'independent' localization length extracted from conductance scaling in Fig. S4 does not provide a fully independent confirmation: it is obtained from the same devices, uses the same exponential fitting form, and shares the assumption that transport is dominated by a single localization length. The manuscript reports only that the two extractions agree 'within the same order of magnitude,' which is a weak quantitative check. A more convincing independent test would be a different measurement or analysis (e.g., magnetotransport, temperature-dependent resistance scaling with a known functional form, or a percolation-based model) that does not presuppose the exponential form of Eq. (5). As it stands, the confirmation is in part circular.","section":"Figure S4 and cross-check of localization length"},{"comment":"The extraction of n_s, mu, and D_eff relies on the full-depletion regime as a zero-density reference (V_dep). The manuscript does not state how V_dep is determined for each device and whether the depletion plateau is actually reached in all devices and at all temperatures. If V_dep varies with channel length (for instance, due to a length-dependent parasitic capacitance or incomplete depletion), the integration limits in Eq. (3) change, producing an artificial length dependence in the effective DOS and chemical potential. The authors should specify the criterion used to identify V_dep, show the raw I_TG/V_BG curves over the full gate-voltage range for every device, and quantify the robustness of the extracted D_eff to the choice of V_dep.","section":"Equations (2)-(3), depletion-limit normalization"}],"minor_comments":[{"comment":"The IGZO composition notation is inconsistent: the main text states In:Ga:Zn ratios of 5:1:1 and 7:1:1, while the Figure 5c caption refers to 'IGZO 311 TFTs.' Please clarify which ratio corresponds to '311' and unify the notation throughout.","section":"Figure 5c and text"},{"comment":"Please indicate whether the plotted points represent single devices or averages over multiple nominally identical devices; if multiple devices were measured, include error bars and the number of devices per channel length.","section":"Figure 3d"},{"comment":"The term 'disorders' is used as a countable noun (e.g., 'suppress disorders'), which is nonstandard in this context; consider using 'disorder' or 'disorder effects' for clarity.","section":"Throughout"},{"comment":"The phrase 'partially transport-active' is not precisely defined. Please specify the operational definition (e.g., the fraction of states contributing to conduction at a given energy, or the criterion used to separate transport-active from screening-active states).","section":"Abstract and text"},{"comment":"The temperature and gate-voltage range of the conductivity scaling data are not stated in the main text or the SI caption. Since the localization length is energy-dependent and temperature-dependent, please include these measurement conditions.","section":"Figure S4"}],"recommendation":"major_revision","confidential_remarks":"The paper addresses a topic of interest to the oxide-semiconductor and mesoscale transport communities, and the eFPT measurement itself appears novel and potentially useful. However, the central quantitative claim (Eq. 5) is currently supported only by fits on a small dataset and by an untested chemical-potential alignment assumption. The authors likely have the raw data (e.g., the I_TG/V_BG curves for different L) to test whether an L-dependent energy offset could explain the apparent exponential suppression; if they include such a robustness analysis, the manuscript could become a strong candidate for publication. The current version, however, does not yet meet the evidentiary bar for the claim of size-dependent band-tail localization."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The paper is a plausible, well-executed measurement campaign with a real new result: geometry-dependent effective DOS mapping in operating oxide TFTs. The eFPT technique itself is established (Eisenstein, Young-Levitov), but applying it to map effective DOS as a function of channel length and temperature is new. The observation that the disorder-dominated band-tail DOS shrinks with L and T is genuinely interesting, and the systematic control experiments (thickness, O2 annealing, In/Ga/Zn ratio) are a nice touch. The paper reads honestly and cites the relevant literature, including the authors' prior Nano Letters work that set up the disorder-dominated transport framework.\n\nThe soft spot is the chemical-potential alignment. Eq. 4 gives mu up to a constant, and they set that constant by assuming a common intrinsic reference at zero gate bias for all devices on the same film. That is load-bearing and untested. If flat-band or depletion-onset voltage varies with L—lateral nonuniformity, doping gradients, process-induced charge—then sampling D_eff at fixed nominal mu actually samples different physical energies. With an Urbach tail and a linear-in-L flat-band shift, you'd get exactly the exponential-in-L D_eff they report, with no localization needed. The paper provides no independent energy reference (C-V flat-band, depletion-onset edge, thickness/doping calibration), so the artifact remains live.\n\nAlso, Fig. 3d shows linear fits without error bars or per-L device counts, and the localization length extraction is an exponential fit to data that are themselves exponential fits. The cross-check via conductance scaling (Fig. S4) is on the same devices and also exponential, so it doesn't break the circularity.\n\nNone of this proves the result is wrong; it means the paper needs revision or supplementary evidence before the claim is solid. If the authors can show that the depletion-onset voltage is L-independent (or that the extracted xi changes with temperature in a way that can't be explained by alignment shifts), that would settle it.\n\nWho this is for: device physicists and oxide-semiconductor people. A serious referee should engage. I'd send it to review, with the alignment issue as the main ask. My own verdict: conditional, not a reject.","headline":"Plausible and potentially useful new measurement campaign, but the central exponential-length claim rests on an untested chemical-potential alignment and error-bar-free fits, so it needs revision before the localization interpretation is solid.","tokens_in":11664,"tokens_out":2242,"would_cite":false,"duration_ms":21197,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"By directly mapping the density of states in working oxide transistors, this paper shows that the transport-active band-tail states shrink exponentially with channel length—a signature of disorder-induced localization that shifts the…","keywords":["oxide semiconductors","thin-film transistors","density-of-states mapping","band-tail states","localization length","quantum capacitance","indium oxide","disorder engineering"],"falsifier":"Take the longest and shortest devices from the same film, measure their intrinsic depletion-onset voltages (where the penetration current plateaus), and re-align the chemical-potential axes using those onsets instead of the zero-bias reference; if the exponential suppression of $D_{\\mathrm{eff}}$ with $L$ survives the re-alignment, the localization interpretation is supported, and if it collapses, the effect is an artifact of misaligned energy scales.","tokens_in":10578,"feed_emoji":"📉","tokens_out":9594,"duration_ms":83760,"temperature":0.7,"pith_summary":"Thin-film oxide transistors are usually described as if their band-tail states were fixed traps that only affect how well the gate switches the device. This paper argues that, in ultrathin In-based oxide channels, a large part of the band tail is instead made of states that become localized as the device gets longer, so the number of states that can actually screen and carry current shrinks exponentially with channel length. The evidence comes from a lock-in electric-field penetration technique that directly maps the density of states in working dual-gate transistors, from depletion to accumulation. If the claims hold, the effective density of states is not a material constant: it depends on device geometry through a localization length, and this size dependence is a new microscopic mechanism behind threshold-voltage roll-off in scaled oxide transistors.","feed_headline":"Oxide TFT band-tail states shrink exponentially as channels lengthen.","feed_subtitle":"Direct DOS mapping ties oxide TFT threshold shifts to disorder localization, not fixed traps.","key_machinery":"The central object is the effective density of states $D_{\\mathrm{eff}}(E,L)$ measured by a dual-gate lock-in technique: an AC back-gate excitation penetrates the thin semiconductor channel and the normalized top-gate current gives the quantum capacitance $C_q = e^2\\,\\mathrm{d}n_s/\\mathrm{d}\\mu = e^2 D(E)$, from which carrier density and chemical potential are integrated. The load-bearing identity is the exponential suppression $D_{\\mathrm{eff}}(E,L) = D_0(E)\\exp[-L/\\xi(E)]$, where $\\xi(E)$ is the energy-dependent localization length; the slope of the $\\ln D_{\\mathrm{eff}}$ versus $L$ plot at fixed energy yields $1/\\xi(E)$. This converts the abstract idea of Anderson localization into a measurable device-level scaling law.","core_discovery":"Using the electric-field penetration technique, the authors extract the quantum capacitance, carrier density, and chemical potential of InOx and IGZO thin-film transistors and resolve four energy regimes: deep trap states, shallow band tails, disorder-dominated tail states, and extended diffusive states. The central quantitative result is that the effective transport-active DOS at fixed energy decays exponentially with channel length, $D_{\\mathrm{eff}}(E,L) = D_0(E)\\,\\exp[-L/\\xi(E)]$, while an independent localization length from conductance scaling falls in the same range. Temperature serves as the cross-check: the disorder-dominated portion of the tail is strongly suppressed at low temperature, whereas the extended states are left nearly unchanged. The same geometry and temperature signatures are reduced by thickening the film, by O$_2$ annealing, and by lowering In content through Ga/Zn substitution, which the authors read as systematic suppression of disorder. Together these observations are used to claim that the threshold-voltage roll-off seen at longer channels in these oxides is a localization effect rather than a contact or static-trap effect.","pith_inferences":["A direct test of the energy-alignment assumption would be to re-derive the $D_{\\mathrm{eff}}$ versus $L$ plot after calibrating each device's chemical-potential axis against its own depletion-onset voltage; if the exponential decay were an alignment artifact, the corrected plot would flatten.","The same eFPT measurement could be applied to amorphous or polycrystalline 2D-material FETs to see whether the extracted $\\xi(E)$ tracks independent measures of disorder such as the optical Urbach energy.","One implication the authors do not develop is that a length-dependent DOS makes the threshold voltage itself scale-dependent, so this localization-induced roll-off should be included in variability analysis of future back-end-of-line integrated oxide transistors."],"forward_implications":["Compact models and scaling projections for oxide TFTs that treat the band-tail DOS as a fixed material property will misestimate threshold voltage in short- and long-channel devices; the DOS must be entered as $D_{\\mathrm{eff}}(E,L)$.","The same film can appear more disordered purely because it was patterned with a longer channel, so material comparisons of band-tail quality need to specify geometry.","At cryogenic temperatures, localization freezes out the disorder-dominated tail states first, meaning cooling amplifies threshold-voltage shifts and on-resistance in oxide TFTs.","Process levers that reduce localization—thicker films, O$_2$ annealing, and Ga/Zn substitution—give concrete paths to recover conventional linear scaling in scaled oxide and other low-dimensional channels.","Because eFPT maps the DOS directly in a working transistor, it can expose disorder-dominated transport in any thin-body FET, not just oxide semiconductors."],"supporting_citations":[{"why":"Defines the disorder-dominated transport regime and the breakdown of Ohm's law in low-dimensional transistors, the framework this paper extends to direct DOS mapping.","marker":"8"},{"why":"Provides the quantum-capacitance and compressibility measurement foundation that the electric-field penetration technique uses to extract the DOS.","marker":"23–25"},{"why":"Introduced the exponential Urbach tail in disordered solids, the band-tail concept that this paper maps as a function of energy.","marker":"10"},{"why":"Supplies the simple band model for amorphous semiconductors in which band-tail and localized states appear.","marker":"11"},{"why":"Establishes localized states near band edges in non-crystalline materials, the physical basis for the disorder-dominated tail regime.","marker":"13"},{"why":"Gives the theoretical result that sufficiently strong disorder removes diffusion, underpinning the assignment of the exponential length dependence to localization.","marker":"14"},{"why":"Shows record-low contact resistance for In2O3 TFTs, supporting the claim that the observed geometry dependence is not contact-limited.","marker":"28"},{"why":"Provides the high-quality scaled InOx transistor platform on which the DOS mapping measurements are performed.","marker":"3"}],"fun_headline_variants":["Direct DOS maps show oxide TFT tails shrink exponentially with length","Shorter oxide TFT channels boost disorder: direct DOS evidence","Oxide TFT threshold shifts tied to exponential tail localization","Size-dependent band-tail collapse seen in oxide TFT direct DOS","Longer oxide channels localize tail states, direct DOS confirms"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The entire length-dependent comparison assumes that every device on the same film has the same chemical potential at zero back-gate bias, so that a fixed gate voltage means the same energy in every channel; if individual devices deplete at different voltages, the reported exponential decay could be an artifact of misaligned energy scales.","fun_headline_variants_meta":{"raw":{"variants":["Direct DOS maps show oxide TFT tails shrink exponentially with length","Shorter oxide TFT channels boost disorder: direct DOS evidence","Oxide TFT threshold shifts tied to exponential tail localization","Size-dependent band-tail collapse seen in oxide TFT direct DOS","Longer oxide channels localize tail states, direct DOS confirms"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000179,"raw_usage":{"total_tokens":1312,"prompt_tokens":968,"completion_tokens":344,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":584,"completion_tokens_details":{"reasoning_tokens":259}},"tokens_in":584,"tokens_out":344,"duration_ms":4181,"temperature":1.0,"reasoning_tokens":259,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T20:10:55.311112+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Take the longest and shortest devices from the same film, measure their intrinsic depletion-onset voltages (where the penetration current plateaus), and re-align the chemical-potential axes using those onsets instead of the zero-bias reference; if the exponential suppression of $D_{\\mathrm{eff}}$ with $L$ survives the re-alignment, the localization interpretation is supported, and if it collapses, the effect is an artifact of misaligned energy scales.","supporting_citations":[],"review_version":1}