Intrinsic Defects, Fluctuations of the Local Shape, and the Photo-Oxidation of Black Phosphorus

Utt, Kainen L.; Rivero, Pablo; Mehboudi, Mehrshad; Harriss, Edmund; Borunda, Mario F.; Sanjuan, Alejandro A. Pacheco; Barraza‐Lopez, Salvador

doi:10.1021/acscentsci.5b00244

Cited by 74 publications

(94 citation statements)

References 67 publications

(176 reference statements)

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“…Typically negative photoconductivity in 2D systems can be associated with the bolometric effect . However, the unusual negative photocurrent observed under longwave UV (365 nm) excitation, in the case of BP is intrinsically material‐related and is associated with the surface adsorbates . It is well known that BP in ambient conditions readily adsorbs oxygen and forms phosphorus oxide species across the crystal surface which can act as charge trap sites .…”

Section: Resultsmentioning

confidence: 99%

“…However, the unusual negative photocurrent observed under longwave UV (365 nm) excitation, in the case of BP is intrinsically material‐related and is associated with the surface adsorbates . It is well known that BP in ambient conditions readily adsorbs oxygen and forms phosphorus oxide species across the crystal surface which can act as charge trap sites . These extrinsic trap sites act as scattering centers under light illumination and reduce the conductance of the device and, hence, are the origin of negative photocurrent.…”

Section: Resultsmentioning

confidence: 99%

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Optically Stimulated Artificial Synapse Based on Layered Black Phosphorus

Ahmed

Kuriakose

Mayes

et al. 2019

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The translation of biological synapses onto a hardware platform is an important step toward the realization of brain‐inspired electronics. However, to mimic biological synapses, devices till‑date continue to rely on the need for simultaneously altering the polarity of an applied electric field or the output of these devices is photonic instead of an electrical synapse. As the next big step toward practical realization of optogenetics inspired circuits that exhibit fidelity and flexibility of biological synapses, optically‑stimulated synaptic devices without a need to apply polarity‑altering electric field are needed. Utilizing a unique photoresponse in black phosphorus (BP), here reported is an all‑optical pathway to emulate excitatory and inhibitory action potentials by exploiting oxidation‑related defects. These optical synapses are capable of imitating key neural functions such as psychological learning and forgetting, spatiotemporally correlated dynamic logic and Hebbian spike‑time dependent plasticity. These functionalities are also demonstrated on a flexible platform suitable for wearable electronics. Such low‐power consuming devices are highly attractive for deployment in neuromorphic architectures. The manifestation of cognition and spatiotemporal processing solely through optical stimuli provides an incredibly simple and powerful platform to emulate sophisticated neural functionalities such as associative sensory data processing and decision making.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Optically Stimulated Artificial Synapse Based on Layered Black Phosphorus

Ahmed

Kuriakose

Mayes

et al. 2019

Small

230

288

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“…This agrees with theoretical studies which predict that intrinsic defect induced photo-oxidation sites lower the chemisorption barrier of BP. 29 As such, the onset of photooxidation occurs most readily in the UV-blue region.…”

Section: Resultsmentioning

confidence: 99%

Degradation of black phosphorus is contingent on UV–blue light exposure

et al. 2017

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Layered black phosphorous has recently emerged as a promising candidate for next generation nanoelectronic devices. However, the rapid ambient degradation of mechanically exfoliated black phosphorous poses challenges in its practical implementation in scalable devices. As photo-oxidation has been identified as the main cause of degradation, to-date, the strategies employed to protect black phosphorous have relied upon preventing its exposure to atmospheric oxygen. These strategies inhibit access to the material limiting its use. An understanding of the effect of individual wavelengths of the light spectrum can lead to alternatives that do not require the complete isolation of black phosphorous from ambient environment. Here, we determine the influence of discrete wavelengths ranging from ultraviolet to infrared on the degradation of black phosphorous. It is shown that the ultraviolet component of the spectrum is primarily responsible for the deterioration of black phosphorous in ambient conditions. Based on these results, new insights into the degradation mechanism have been generated which will enable the handling and operating of black phosphorous in standard fabrication laboratory environments.

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“…12,13 As one of the most stable polymorphs among all phosphorus allotropes, 14 according to the thermodynamic criteria, phosphorene starts to disintegrate quickly at ambient condition, which is generally ascribed to effects from external molecules. 15,16 While protecting phosphorene from the environmental influence via capping layers was found to effectively improve its stability, 17,18 intrinsic structural stability dictated solely by atomic defects like vacancies then becomes a fundamental descriptor for its applications. Recent compelling in-situ experiment in vacuum demonstrates a fast evolution of structure with temperature, 19 in which atomic sublimation occurring without melting process.…”

Section: Introductionmentioning

confidence: 99%

Highly Itinerant Atomic Vacancies in Phosphorene

et al. 2016

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Using detailed first-principles calculations, we investigate the hopping rate of vacancies in phosphorene, an emerging elemental 2D material besides graphene. Our work predicts that a direct observation of these mono-vacancies (MVs), showing a highly mobile and anisotropic motion, is possible only at low temperatures around 70 K or below where the thermal activity is greatly suppressed. At room temperature, the motion of a MV is sixteen orders faster than that in graphene, because of the low diffusion barrier of 0.3 eV. Built-in strain associated with the vacancies extends far along the zigzag direction while attenuating rapidly along the armchair direction. We reveal new features of the motion of di-vacancies (DVs) in phosphorene via multiple dissociation-recombination processes of vacancies owing to a small energy cost of ~ 1.05 eV for the splitting of a DV into two MVs. Furthermore, we find that uniaxial tensile strain along the zigzag direction can promote the motion of MVs, while the tensile strain along the armchair direction has the opposite effect. These itinerant features of vacancies, rooted in the unique puckering structure facilitating bond reorganization, enable phosphorene to be a bright new opportunity to broaden the knowledge of the evolution of vacancies, and a proper control of the exceedingly active and anisotropic movement of the vacancies should be critical for applications based on phosphorene.

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Intrinsic Defects, Fluctuations of the Local Shape, and the Photo-Oxidation of Black Phosphorus

Cited by 74 publications

References 67 publications

Optically Stimulated Artificial Synapse Based on Layered Black Phosphorus

Optically Stimulated Artificial Synapse Based on Layered Black Phosphorus

Degradation of black phosphorus is contingent on UV–blue light exposure

Highly Itinerant Atomic Vacancies in Phosphorene

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