Boron Vacancies Causing Breakdown in 2D Layered Hexagonal Boron Nitride Dielectrics

Ranjan, Alok; Raghavan, Nagarajan; Puglisi, Francesco Maria; Mei, Sen; Padovani, Andrea; Larcher, Luca; Shubhakar, K.; Pavan, Paolo; Bosman, Michel; Zhang, X. X.; O’Shea, S. J.; Pey, K. L.

doi:10.1109/led.2019.2923420

Cited by 20 publications

(21 citation statements)

References 21 publications

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“…However, we highlight that a large difference and spread in β is expected if the sample being tested has a wide variation in h-BN thickness. 44 Further, CVD-grown h-BN films are known to have many other sources of variability. 35,45 These include local defect density variations, grain boundaries, and the roughness of the bottom electrode which can skew the V SBD,h-BN distributions.…”

Section: Resultsmentioning

confidence: 99%

Localized Probing of Dielectric Breakdown in Multilayer Hexagonal Boron Nitride

Ranjan

O’Shea

Bosman

et al. 2020

ACS Appl. Mater. Interfaces

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Hexagonal boron nitride (h-BN) has emerged as a promising 2D/layered dielectric owing to its successful integration with graphene and other 2D materials, although a coherent picture of the overall dielectric breakdown mechanism in h-BN is yet to emerge. Here, we have carried out a systematic study using conduction atomic force microscopy to provide insights into the process of defect generation and dielectric degradation in the progressive breakdown (PBD) and hard breakdown (HBD) stages in 2−5 nm thick chemical vapor deposition (CVD)-grown multilayer h-BN films. The PBD and HBD regimes show different behaviors. Under electrical stress in the PBD stage, defects are generated progressively in the h-BN, leading to a gradual reduction of the effective barrier resistance and continuous soft breakdowns (SBDs) of the dielectric material. Random telegraph noise nano-spectroscopy shows that low frequency noise becomes dominant after an SBD event due to the creation of additional defects around the percolation path. We also observe a wide variation in the current−voltage (I−V) breakdown plots in the PBD stage, giving rise to non-Weibull statistical distribution of the breakdown voltage. We attribute this observation to the significant thickness inhomogeneity in the CVD films. At HBD, h-BN materials are always physically removed from the film, leading to the formation of pits at the breakdown location. Interestingly, pit formation is also occasionally observed in the PBD stage under very low current compliances, suggesting that breakdown may proceed by a mixture of defect generation and material removal in h-BN CVD films.

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Section: Resultsmentioning

confidence: 99%

Localized Probing of Dielectric Breakdown in Multilayer Hexagonal Boron Nitride

Ranjan

O’Shea

Bosman

et al. 2020

ACS Appl. Mater. Interfaces

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“…The currents driven by the memristors increased over time until the dielectric breakdown (DB) of the oxide was triggered (Figure 1b), as expected. [ 36 ] Then, in fresh devices, we applied sequences of RVS in order to introduce certain amount of defects in the insulator (Figure 1c), and after that, we applied again CVS at different biases. The Ni/Al 2 O 3 /Au never exhibited RTN; on the contrary, the Ni/HfO 2 /Au samples exhibited RTN current signals fluctuating between ≈24 and ≈60 µA when a CVS of 4.5 V was applied (Figure 1d), but only after an RVS from 0 to 8 V was applied (Figure 1c).…”

Section: Materials‐based Rtn Analysismentioning

confidence: 99%

“…An RTN current signal is defined as the current signal that exhibits stochastic fluctuations between two or more levels at random and unpredictable times [ 7 ] ; this phenomenon has been observed in multiple solid‐state electronic devices (e.g., point contact diodes, [ 8 ] metal‐oxide‐semiconductor field‐effect transistors [ 9 ] ), and it is related to the random capture and emission of charge carriers at the atomic defects in dielectrics and semiconductors, as well as at their interfaces with metals. [ 10 ] Two‐level RTN signals are produced by one single defect within the entire MIM‐like memristor, [ 11 ] while multilevel RTN signals are formed by more than one. [ 12 ]…”

Section: Introductionmentioning

confidence: 99%

Random Telegraph Noise in Metal‐Oxide Memristors for True Random Number Generators: A Materials Study

Zanotti

Wang

et al. 2021

Adv Funct Materials

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Some memristors with metal/insulator/metal (MIM) structure have exhibited random telegraph noise (RTN) current signals, which makes them ideal to build true random number generators (TRNG) for advanced data encryption. However, there is still no clear guide on how essential manufacturing parameters like materials selection, thicknesses, deposition methods, and device lateral size can influence the quality of the RTN signal. In this paper, an exhaustive statistical analysis on the quality of the RTN signals produced by different MIM‐like memristors is reported, and straightforward guidelines for the fabrication of memristors with enhanced RTN performance are presented, which are: i) Ni and Ti electrodes show better RTN than Au electrodes, ii) the 50 μm × 50 μm devices show better RTN than the 5 μm × 5 μm ones, iii) TiO2 shows better RTN than HfO2 and Al2O3, iv) sputtered‐oxides show better RTN than ALD‐oxides, and v) 10 nm thick oxides show better RTN than 5 nm thick oxides. The RTN signals recorded have been used as entropy sources in high‐throughput TRNG circuits, which have passed the randomness tests of the National Institute of Standards and Technology. The work can serve as a useful guide for materials scientists and electronic engineers when fabricating MIM‐like memristors for RTN applications.

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“…A straightforward type of device for this purpose is a metal–insulator–metal (MIM) configuration. To date, several reports have been published to study the electrical transport and BD properties of MIM structures based on 2D h-BN films. − Among these studies, many relied on the conductive atomic force microscopy technique to extract electrical properties. − While this method is quite effective, the contact area cannot be precisely determined, leading to a limited understanding of electron tunneling through the h-BN barriers. Although some other reports have adopted MIM devices using direct metal or graphene contacts, ,− most are based on thicker h-BN films of a few layers to a few tens of layers.…”

Section: Introductionmentioning

confidence: 99%

Study of Direct Tunneling and Dielectric Breakdown in Molecular Beam Epitaxial Hexagonal Boron Nitride Monolayers Using Metal–Insulator–Metal Devices

Cui

Tian

et al. 2020

ACS Appl. Electron. Mater.

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Direct tunneling and dielectric breakdown in molecular beam epitaxial hexagonal boron nitride (h-BN) monolayers were studied based on Ni/h-BN/Ni metal−insulator−metal (MIM) device structures. Effective tunneling areas are orders of magnitude smaller than physical areas of the devices. Statistical Weibull analysis of the breakdown characteristics shows that the breakdown area-scaling law applies to effective areas rather than physical areas of the devices. The h-BN monolayer MIM devices can sustain repeated dc voltage sweeping stresses up to 85 times under an extremely high compliance current of 100 mA, and the critical electric field is determined to be at least 11.8 MV/cm, demonstrating high dielectric strength and reliability of these h-BN monolayers. The mechanism of breakdown and recovery of the h-BN monolayer MIM devices is also discussed.

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Boron Vacancies Causing Breakdown in 2D Layered Hexagonal Boron Nitride Dielectrics

Cited by 20 publications

References 21 publications

Localized Probing of Dielectric Breakdown in Multilayer Hexagonal Boron Nitride

Localized Probing of Dielectric Breakdown in Multilayer Hexagonal Boron Nitride

Random Telegraph Noise in Metal‐Oxide Memristors for True Random Number Generators: A Materials Study

Study of Direct Tunneling and Dielectric Breakdown in Molecular Beam Epitaxial Hexagonal Boron Nitride Monolayers Using Metal–Insulator–Metal Devices

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