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Cited by 10Advanced Memory and Neural ComputingPhase-change materials and chalcogenidesFerroelectric and Negative Capacitance Devices

Polarity-dependent memory switching effects in the Ti/CdxPb1-xS/Ag system

Open access
Upadhyaya, H M, Chandra, S·1995·Semiconductor Science and Technology
DOI 10.1088/0268-1242/10/3/016
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Abstract

Polarity-dependent memory switching has been observed in the system Ti/Cd x Pb 1-x S/Ag for x=0.575 to 0.895. The material Cd x Pb 1-x S prepared by a chemical bath deposition technique, possessed excess Cd and Pb clusters. A polyfilamentary model based on whisker growth due to the aggregation of Cd, Pb and Ag (arising from the electrode interface) has been suggested to explain the memory switching characteristics in our system. The 'growth' of filamentary whiskers followed by their 'rupture' at higher injection currents due to Joule heating is assumed to give rise to the switching action.

AI snapshot

Written from the paper’s full text.

TL;DR

The Ti/CdxPb1-xS/Ag planar device shows polarity-dependent memory switching, with ON and OFF states retained for days and reversed only by changing the applied polarity. The behavior is attributed to formation and rupture of metallic filaments in unintentionally grown interfacial oxide layers.

Key findings

  • For CdxPb1-xS compositions with x below 1, the device exhibits memory-type switching in both polarities; pure CdS (x = 1) showed no switching and only a monotonic current increase with voltage.
  • Initial I-V cycling produces both current-controlled and voltage-controlled negative-resistance thresholds; after 20–30 cycles, thresholds stabilize and only VCNR-type, figure-eight-like switching remains.
  • Low-current operation below about 5 mA and up to roughly 0.8 V is diode-like; higher currents cause instabilities and switching. ON/OFF states persist for days and require reverse polarity to toggle.
  • The proposed mechanism is a polyfilamentary model: Ag from the electrode and excess Cd/Pb in the film grow filaments, giving CCNR switching, while Joule-heating-induced filament rupture gives VCNR switching.

Methods

  • CdxPb1-xS films were deposited on cleaned Ti substrates by chemical bath deposition using CdSO4, thiourea, Pb(NO3)2, and NH4OH; film thickness was about 2.0 µm with roughly ±0.3 µm surface variation. Ag dots about 2 mm in diameter were vacuum-evaporated, and Cu wire was attached with silver paste and epoxy.
  • I-V characteristics were measured with a regulated DC supply and a 10 kΩ helipot for polarity reversal; current was measured as a voltage across a calibrating resistor, and voltage/current were recorded on an X-Y recorder.
  • The switching behavior was interpreted using an MIS/MSM band-diagram picture and a polyfilamentary forming/rupture model, supported by prior characterization of excess Cd/Pb and n-type conduction in the films.

Limitations

  • Stated: the unintentionally grown oxide layers were not directly measured and were estimated as less than 50 Å; electrode contact definition complicates interpretation; the forming mechanism is described as closer to conjecture than an established process.
  • Stated: asymmetry in ON/OFF states across polarities is attributed to different barrier heights for Ti and Ag.
  • Evident: filament growth and rupture are inferred qualitatively without direct filament imaging; the text reports different composition ranges in the abstract and results, limiting certainty about the exact switching composition window.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1088/0268-1242/10/3/016

Cites

41 of 41 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

1 of 7 cited sources checked · 0 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    The CdxPb1-xS material produced by chemical bath deposition contained excess Cd and Pb clusters.

    “The material CdxPbl_,S prepared by a chemical bath deposition technique; possessed excess Cd and Pb clusters.”
    • Also stated in: § 3. Results and discussion · boosted
      “As discussed in section 1, the semiconductor Cd,Pbl-,S (x = 0.575) invariably possessed Cd and Pb metallic excess as evidence by optical microscopy, XRD, EDAX and optical absorption studies reported earlier by us [29].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [29] Upadhyaya H M, 1994, J. Mater. Sci. source

      Semantic Scholar returned no full-text snippets for Upadhyaya and Chandra (1994) across two queries, so the claim about excess Cd and Pb clusters cannot be checked against the cited paper. A different paper, “Morphological and structural features of the CdxPb1−xS films obtained by CBD from ethylenediamine-citrate bath,” has a 0.716-score match about excess cadmium associated with amorphous CdS, but it does not report excess Cd and Pb clusters. That partial match is insufficient to confirm the claim or establish misattribution. (LLM, conf=0.68)

      Experimental — accuracy not yet measured
  • Findingown data

    Initial I-V shows both CCNR and VCNR type switching.

    “The initial I-V shows both CCNR and VCNR type switching.”
    Quote in the paperSubstantial claim
  • Findingown data

    For x = 1 (pure CdS), no switching behavior was seen.

    “For x = 1 (i.e. for pure CdS), no switching behaviour was seen and there is a monotonic increase of current with voltage in both the polarities.”
    Quote in the paperSubstantial claim
  • Findingown data

    A reverse-polarity voltage is required to change the device's memory state.

    “In order to change the memory states, a reverse polarity voltage has to be applied (taking the device from the first to the third quadrant of I-V characteristics or vice versa).”
    • Also stated in: § 4. Conclusion · plain
      “The two stable states (OFF and ON) are found to occur at both polarities and the reversal of states OFF to ON and vice versa takes place only when the polarity of the potential applied to the device is changed.”
    Quote in the paperSubstantial claim
  • Findingown data

    The device exhibited memory-type switching in both polarities after multiple I-V cycles.

    “The device with the configuration described above showed memory-type switching in both polarities after passing through multiple I-V cycling.”
    Quote in the paperSubstantial claim
  • May combine two claims. 12
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingown data

    Initial I-V cycling shows two thresholds in each polarity for OFF-to-ON and ON-to-OFF, with exact threshold values changing on cycling and not quite symmetrical.

    “(i) At the initial stages of I-V c y c h g there are two thresholds in each polarity characterizing respectively OFF to ON and ON to OFF states marked as F, and F; (F2, F; in reverse polarity) in figure 3(c).The exact threshold voltages/currents corresponding to F,, F, and Fz, F; keep changing on cycling.The switching thresholds are not quite symmetrical in either the polarity but the general”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    At currents below 5 mA and voltages below about 0.8 V, the device behaves like a poor diode.

    “(i) Figure 3 level (c 0.8 V) so that the current flowing through the device did not exceed 5 mA.The behaviour is typical of a diode (though poor).”
    • Also stated in: § 3.1. Mechanistic aspects of switching behaviour · plain
      “When the device was cycled, taking the precaution that the current was less than 5 mA, then a typical diode behaviour was obtained with a poor ideality factor.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The device's ON and OFF states are memory-type and retain their conductivity for about a few days.

    “The switching states ON (high conducting) and OFF (low conducting) have been found to be of the 'memory type' showing retention of the respective conductivity states for a long time (-a few days).”
    • Also stated in: § 4. Conclusion · plain
      “Both the states 'OFF' and 'ON' can be retained for days, which is typical of memory devices.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The CCNR threshold keeps shifting on cycling and ultimately disappears after many cycles.

    “As stated earlier, the CCNR threshold keeps on shifting on cycling, ultimately disappearing after many cycles.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    After 20-30 cycles, the switching thresholds become stable and the I-V switching is repeatable.

    “(iv) After 20-30 cycles, the switching thresholds acquire stable values and the I-V switching is repeatable (figure 3(d)).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    At currents above 5 mA, the I-V curve becomes unstable and tends not to be diode-like.

    “(ii) Figure 3 (b) shows the behaviour when the voltage was increased beyond 0.8 V so that the level of current flowing through the device was > 5 mA.The I-V curve starts showing instabilities and the behaviour at these injection levels has a tendency not to be 'diode like'.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Each cycle leaves some filaments in the insulating layer, so subsequent cycling shows lower thresholds for CCNR switching.

    “Each cycle leaves some filaments in the insulating layer.Therefore, subsequent cycling would show lower thresholds for CCNR switching (figure 4(c')).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Once each filament bridges the gap between electrodes, electronic conduction begins and Joule heating may occur.

    “Once each filament bridges the gap between the electrodes, electronic conduction begins and Joule heating may occur.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The poor ideality factor is expected because two depletion layers exist on either side, and when one junction is forward biased the other is reverse biased.

    “The poor ideality factor is expected because of the presence of two depletion layers on either side.When one junction is getting forward biased, the other becomes reverse biased and hence the currents in both the oolarities would not be much”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    As bias increases, filaments grow, and some from either side may become long enough to drastically reduce the effective path in the insulator, giving increased current or a high-conductivity state (CCNR switching).

    “As V increases, the filaments grow further and further as shown in figure 4(c).Some of the filaments growing from either side may become so long that the effective path in the insulator is drastically reduced (giving rise to increased current or a high-conductivity state).This is CCNR type switching shown in figure 4(c').”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationnone given

    At low currents, MS and MIS behavior cannot be distinguished, so the diode behavior can be understood as either MS or MIS junctions at the two sides.

    “This can be understood either in terms of MS or MIS (where I is an unintentionally grown insulating layer) junction formed at the two sides as shown in the figure 2(a), because MS and MIS behaviour at low currents cannot different.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Unintentionally grown oxide insulating layers I1 and I2 exist at both metal-semiconductor interfaces.

  • May combine two claims.

    Interpretationreasoning

    If voltage is increased further, filaments may rupture and the device may go to a low-conductivity state (VCNR switching).

    “If the voltage is increased further, then, for reasons described earlier, the filaments may rupture as shown in figure 4(d) and the device may go again to a low-conductivity state which is the VCNR type of switching.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The growth of filamentary whiskers followed by their rupture at higher injection currents due to Joule heating gives rise to the switching action.

  • May combine two claims.

    Interpretationreasoning

    Filaments may fracture and cease to contribute to conduction, and can re-form under suitable conditions.

    “The filaments may fracture and cease to contribute to the conduction and can also re-form under suitable conditions related to the basic filamentforming process.”
    Quote in the paperSubstantial claim
13 of 13

  • The authors state this as an assumption.

    Unintentionally grown oxide insulating layers I1 and I2 exist at both metal-semiconductor interfaces.

    “There is always the possibility of the presence of some unintentionally grown oxide insulating layers (1, and 12) on both the metal-semiconductor interfaces giving the following configuration (see figure 2(a)) MI (Ti) 111 ICd,Pbl-,S ILIMZ(Ag).”
    “plausible interpretation lies in the assumption of the presence of unintentionally grown insulating layers I, and 12 in which a 'forming process' occurs on voltage cycling which is responsible for the switching thresholds.”

  • The authors state this as an assumption.

    The growth of filamentary whiskers followed by their rupture at higher injection currents due to Joule heating gives rise to the switching action.

    “The 'growth' of filamentary whiskers followed by their 'rupture' at higher injection currents due to Joule heating is assumed to give rise to the switching action.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Similar devices to those in the 2008 claim were already discovered in 1995.

    “Similar devices were already discovered in 19958, but those early discoverers do still not think that their devices are real memristors.”

    From The Missing Memristor has Not been Found (2015) · cites this paper as [8]

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Reported switching compositions exceed the abstract's range

    Minor

    The abstract limits observed switching to x values no higher than 0.895, but the results report similar switching at x = 0.935, 0.955, and 0.985.

1 of 1

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Shaw M P, 1971, Appl. Phys. Lett., 19, 24

Cited by

Sorted by citations

Related

Authors
Upadhyaya, H. M., & Chandra, S.
Affiliations
Banaras Hindu University (IN)
ORCID
Upadhyaya, H M
Venue
Semiconductor Science and Technology
Publisher
IOP Publishing
Published
1995-03-01
Volume
10
Issue
3
Pages
332-338
ISSN
  • 0268-1242 (ISSN-L)
  • 1361-6641
DOI
10.1088/0268-1242/10/3/016
OpenAlex
W1989325272
Semantic Scholar
402f8ae210fb5613797ef659ce96e89abe9db25e
Cited by
10
References
41
Citations by year
2025: 2 · 2020: 1 · 2015: 2 · 2012: 1
FWCI
0.00
Type
journal article
Language
en
Open access
Locations
Semiconductor Science and Technology (publishedVersion)
Topics
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Advanced Memory and Neural Computing
  • Physical Sciences › Materials Science › Materials Chemistry › Phase-change materials and chalcogenides
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Ferroelectric and Negative Capacitance Devices
Keywords
memory switching, chemical bath deposition, whisker growth, Joule heating, electrode interface

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