The fundamental building block of an artificial spiking neural network (SNN) is an element which can effectively mimic a biological neuron. There are several electronic and spintronic devices which ...have been demonstrated as a neuron. But the main concern here is the energy consumption and large area of those artificial neurons. In this letter, we propose and demonstrate a highly scalable and CMOS compatible bulk FinFET with an <inline-formula> <tex-math notation="LaTeX">{n}^{+} </tex-math></inline-formula> buried layer for ultra low energy artificial neuron using well calibrated TCAD simulations. The proposed device shows the signature spiking frequency versus input voltage curve of a biological neuron. The energy per spike of the integrate block of the proposed leaky integrate and fire (LIF) neuron is <inline-formula> <tex-math notation="LaTeX">{6.3}~\textit {fJ} </tex-math></inline-formula>/spike which is the minimum reported till date.
We propose a novel highly scalable source-drain-junction-free field-effect transistor that we call the bulk planar junctionless transistor (BPJLT). This builds upon the idea of an isolated ultrathin ...highly doped device layer of which volume is fully depleted in the off-state and is around flatband in the on-state. Here, the leakage current depends on the effective device layer thickness, and we show that with well doping and/or well bias, this can be controllably made less than the physical device layer thickness in a bulk planar junction-isolated structure. We demonstrate by extensive device simulations that these additional knobs for controlling short-channel effects reduce the off-state leakage current by orders of magnitude for similar on-state currents, making the BPJLT highly scalable.
We evaluate the impact of band-to-band tunneling (BTBT) on the characteristics of n-channel junctionless transistors (JLTs). A JLT that has a heavily doped channel, which is fully depleted in the off ...state, results in a significant band overlap between the channel and drain regions. This overlap leads to a large BTBT of electrons from the channel to the drain in n-channel JLTs. This BTBT leads to a nonnegligible increase in the off-state leakage current, which needs to be understood and alleviated. In the case of n-channel JLTs, tunneling of electrons from the valence band of the channel to the conduction band of the drain leaves behind holes in the channel, which would raise the channel potential. This triggers a parasitic bipolar junction transistor formed by the source, channel, and drain regions induced in a JLT in the off state. Tunneling current is observed to be a strong function of the silicon body thickness and doping of a JLT. We present guidelines to optimize the device for high on-to-off current ratio. Finally, we compare the off-state leakage of bulk JLTs with that of silicon-on-insulator JLTs.
In this work, a nanosecond green laser (532 nm) is used to generate narrow openings by removing an ultra-thin (85 nm) SiN
x
layer that is coated on a silicon substrate for application in the ...fabrication of Passivated Emitter and Rear Contact (PERC) solar cells. An experimental analysis is presented to identify the optimal range of laser parameters for an efficient ablation with minimal damage to the silicon substrate. The ablated samples were characterized using a 3D profilometer to obtain the surface profiles and scanning electron microscope imaging to observe the surface quality. Further, energy-dispersive X-ray line analysis and atom probe tomography were performed to evaluate the nitrogen content on the surface and along the depth, respectively. The experimental results suggest that the SiN
x
layer starts to ablate only above a threshold laser fluence of 1.4 J/cm2, while the surface bulged out for laser fluence slightly below the ablation threshold. The central part of the ablated region was clean with a negligible nitrogen concentration at the surface, about ∼0.03% at a fluence of 2.4 J/cm2. Nitrogen concentration reduces continuously and almost becomes zero at 80 nm depth, suggesting complete ablation of the SiN
x
layer for establishing electrical contacts. The ablation width was close to the laser spot diameter only at lower values of the laser fluence. The lowest value of ablation depth was about 180 nm, suggesting that only about 95 nm layer of the silicon is ablated. The study demonstrates that nanosecond laser ablation is a potential technique for ablation of the SiN
x
layer of PERC solar cells but requires choosing the optimal parameters.
Poly(dimethylsiloxane) (PDMS) has been used extensively for microfluidic components and as substrates for biological applications. Since the native nature of PDMS is hydrophobic it requires a ...functionalization step for use in conjunction with aqueous media. Commonly, oxygen plasma treatment is used for the formation of hydrophilic groups on the surface. However, the hydrophilic nature of these surfaces is short lived and the surfaces quickly revert back to their original hydrophobic state. In this work, branched-polyethylenimine (b-PEI) was used for long term modification of plasma treated PDMS surface. Contact angle, X-ray photoelectron spectroscopy (XPS) and Atomic force microscopy (AFM) were used for characterization of the modified surfaces and their stability with time was studied. The results obtained demonstrate that comparatively higher stability, hydrophilic, positively charged surfaces can be obtained after b-PEI treatment. These b-PEI treated PDMS surfaces can be used as fluidic channels for the separation of molecules as well as a substrate for the adherence of bio-molecules or biological cells.
A photon-initiated chemical route for hydroxylation of CVD graphene and exfoliated graphene is presented. Hydroxyl functionalities have been bonded covalently to exfoliated and CVD graphene by ...treating the graphene with H2O2 in the presence of UV light. Back-gated graphene field effect transistors fabricated from hydroxyl functionalized graphene shows p-type doping and mobility in the range of 1000 cm2 V−1 s−1 which is much higher than reported in graphene oxide and reduced graphene oxide. Vacuum stability of hydroxyl functional groups is demonstrated by keeping hydroxyl functionalized graphene in vacuum for 22 h and comparing the electrical characteristics. As a further proof of –OH functionalization, we demonstrate the deposition of Al2O3 by atomic layer deposition, which is not possible on pristine graphene.
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A simple yet reproducible method to deposit high quality aluminium oxide (AlOx) film by spray coating is presented. Excellent thickness and refractive index uniformity is demonstrated. The AlOx film ...was found to be nearly stoichiometric with an oxygen to aluminium ratio of 1.7 from X-ray photoelectron spectroscopy (XPS) measurements. An interfacial layer with thickness of about 2 nm was observed in transmission electron microscopy analysis. The interfacial layer was determined to be aluminium silicate from XPS data. Electrical characterization of the films on Czochralski (Cz) p-type silicon yielded dielectric constant of 6.5 and mean breakdown field of 4.7 MV cm−1. Interface state density of 8.7×1010 eV−1cm−2 and fixed charge density of −5.5×1012 cm−2 were obtained from the electrical characterization of metal insulator semiconductor capacitors. The excellent interface quality with low interface state density and high negative charge is suitable for passivation of p-type silicon in solar cell applications. Effective surface recombination velocity of 12 cm s−1 and 48 cm s−1 were obtained for Cz p-type silicon surface for annealing temperature of 750°C and 790°C respectively without the use of capping layer.
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We experimentally explored vertical mounting of bifacial modules of different bifacialities for mitigating soiling in Mumbai, where the dust accumulation rate in terms of energy loss per day can be ...as much as 0.45%. Bifaciality is commonly referred to the ratio of the back side value to the front side value of any of the performance parameters I sc , P max , or ῃ. The energy loss due to soiling in vertically mounted bifacial modules and monofacial and bifacial modules mounted at the latitude angle are compared. The experiments reveal that the vertically mounted bifacial modules have nearly zero soiling loss; bifacial modules mounted at latitude angle with 90% bifaciality have lower soiling rate; the energy yield of vertically mounted bifacial modules with 90% bifaciality can exceed that of bifacial modules mounted at latitude angle after three weeks if the modules are left to soil without cleaning; the peak temperature of operation of vertically mounted bifacial modules is seen to be 15 °C lower than that of bifacial modules mounted at latitude angle, implying potential benefits in long-term reliability and performance ratio; combining vertically mounted bifacial modules and bifacial modules mounted at latitude angle, a nearly flat, extended generation profile can be obtained.
Thermally grown SiO 2 is widely used for silicon surface passivation in solar cells and other applications due to excellent interfacial properties. SiO 2 films with thickness in the range of 17 nm ...deposited by industrially viable spray-coating technique on both n- and p-type silicon are reported. Low values of interface state density of <inline-formula> <tex-math notation="LaTeX">{1.4}\times {10}^{{10}} </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{2}} </tex-math></inline-formula>eV<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{1}} </tex-math></inline-formula> on n-type and <inline-formula> <tex-math notation="LaTeX">{2.0}\times {10}^{{10}} </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{2}} </tex-math></inline-formula>eV<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{1}} </tex-math></inline-formula> on p-type were achieved. Fixed oxide charges in the range of 7.1-<inline-formula> <tex-math notation="LaTeX">{9.4}\times {10} ^{{11}} </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{2}} </tex-math></inline-formula> and 3.9-<inline-formula> <tex-math notation="LaTeX">{6.5}\times {10} ^{{11}} </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{2}} </tex-math></inline-formula> on n- and p-type, respectively, are obtained. Excellent passivation results in the effective surface recombination velocity of 0.97 cms<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{1}} </tex-math></inline-formula> and 8.07 cms<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{1}} </tex-math></inline-formula> at minority carrier concentration of <inline-formula> <tex-math notation="LaTeX">10^{{15}} </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{3}} </tex-math></inline-formula> on n- and p-type Czochralski silicon, respectively, without the use of capping layer. SiO 2 film exhibits dielectric breakdown field strength of 4.3 MVcm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{1}} </tex-math></inline-formula> and 5.6 MVcm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{1}} </tex-math></inline-formula> and leakage current density of <inline-formula> <tex-math notation="LaTeX">{2.2}\times 10 ^{\boldsymbol -{8}} </tex-math></inline-formula> Acm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{2}} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">{1.1}\times {10} ^{\boldsymbol -{8}} </tex-math></inline-formula> Acm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{2}} </tex-math></inline-formula> at 1 MVcm<inline-formula> <tex-math notation="LaTeX">^{\boldsymbol -{1}} </tex-math></inline-formula> on n- and p-type silicon, respectively. These values are superior to sol-gel-based SiO 2 films reported previously and are comparable to or better than those reported for other methods for the growth or deposition of SiO 2 on silicon. Amorphous nature of the film is validated by high-resolution transmission electron microscopy (TEM). The X-ray photoelectron spectroscopy (XPS) analysis shows nearly stoichiometric SiO x film.
•The highlights of the present work can be summarized in the form of a few bullet points, as in the following:•Graphene is a fascinating material for micro and nano devices but fracture arises during ...device fabrication or graphene processing, hinder the properties of graphene.•Another reason of fracture in graphene devices is electrical breakdown due to resistive heating.•Reconstruction of graphene and GNRs are necessary for electronics applications of graphene.•The fractured graphene is reconstructed by methane gas treatment at high temperature.•Physical characterization techniques like SEM and AFM confirm the healing of cracks. Graphene layers are investigated before breakdown and after reconstruction of fractured graphene by Raman Spectroscopy.•Analysis of current-voltage characteristics before breakdown and after reconstruction exhibit restoration of current values.•Methane gas treatment method is highly scalable and more cost-effective than e-beam irradiation for reconstruction of graphene and GNRs.
Reconstruction of fractured graphene is demonstrated by methane gas exposure at 850 °C. Graphene was fractured by electrical stress. Reconstruction of the fracture was confirmed by electrical measurements, atomic force microscopy and scanning electron microscopy. Proposed process could be used for reconstruction of graphene after device fabrication in large scale applications.
