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We report an ultralow power consuming and forming-free hybrid flexible resistive random access memory device fabricated with poly(4-vinylphenol) (PVP):MoS2 composite and HfO x bilayer, exhibiting threshold switching with ultralow ON-current of 500 nA. While the higher concentration of MoS2 imparted the higher leakage current in the devices, the lower concentration devices exhibited decent switching with set and reset powers as low as 270 and 0.1 nW, respectively. The ultralow switching current indicates the formation of multiple weak nanosized conductive filaments created due to electromigration of Ag atoms under external bias. Moreover, heating temperature-dependent study of switching behavior confirms the metallic nature of the filament as the low resistance state (LRS) current falls significantly with rising temperature. Furthermore, these devices exhibited remarkable mechanical strength on flexible substrate with demonstration of nondestructive switching characteristics at a bending radius as low as 2.5 mm and after 100 consecutive compressive and tensile strain cycles at ±5-mm radius. The ultralow switching current with high flexibility indicates the capability of devices for advancement toward future low-power flexible memories and computing systems.

Resistive switching behavior of poly (4-vinylphenol):graphene oxide (PVP:GO) composite and ultrathin HfO x hybrid bilayer was explored for developing high-performance flexible resistive random access memory (RRAM) devices. These devices, fabricated with a PVP:GO equivolume solution spin-coated and atomic layer deposited ultrathin HfO x as an active bilayer, exhibited excellent bipolar switching behavior with set and reset voltages as low as 0.6 and −1.46 V, ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ of >105, and ac and dc switching endurance of over 1400 and 800 cycles, respectively. The same device configuration realized over a flexible polyethylene terephthalate (PET) substrate exhibited a memory window of >103 even after undergoing large mechanical strain (correspoding to a 5-mm bending radius). In addition, after 150 cumulative cycles of consecutive tensile and compressive strain at a 5-mm bending radius, flexible RRAMs demonstrated a clear memory window of $4\times 10^{{3}}$ for 104 s. Overall, the incorporation of GO into the PVP solution resulted in achieving better control over conductive filament (CF) growth and, therefore, improved repeatability and reliability. This article indicates that the strategy of incorporating composite and organic–inorganic active bilayer can lead toward the development of high-performance flexible RRAMs.

Reducing the operating voltage and processing temperature are the crucial factors in the progression of organic field-effect transistors (OFETs) in flexible portable applications. Here, we have dem...

Organic FETs (OFETs) with bilayer dielectric poly(4-vinylphenol) (PVP)/HfO2 and polyvinyl alcohol (PVA)/HfO2 were fabricated on a flexible low-cost Kapton tape substrate with TIPS -pentacene:polystyrene as an active layer. The devices exhibited average and maximum field-induced mobility of 0.25(±0.10) and 0.37 cm $^{{{2}}}\text{V}^{{-{1}}}\,\,\text{s}^{{-{1}}}$ for PVP/HfO2 devices, and 0.35(±0.18) and 0.69 cm $^{{{2}}}\text{V}^{{-{1}}}\,\,\text{s}^{{-{1}}}$ for PVA/HfO2 devices, respectively, with low threshold voltage and ${I}_{ \mathrm{\scriptscriptstyle ON}}$ to ${I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio approaching $10^{{{4}}}$ for both types of devices. Overlapping transfer multiple scans with very less performance variation under ambient conditions were observed. The devices were found to be fairly stable even when electrical stress was applied after a period of 5 months. Devices exhibited small degradation in ${I} _{{\text {DS}}}$ and small $\Delta {V} _{{\text {TH}}}$ with high degree of reliability and small performance spreads under combined effects of ambient exposure over a period of 5 months and successive electrical stress. In addition, inverter based on these OFETs with external load was also demonstrated.

In this work, a combination of a thin layer of Copper (II) phthalocyanine (CuPc) and TIPS-pentacene crystal was used to enhance the photo-sensing spectrum of photo- sensitive organic field-effect transistors (photo-OFETs). In TIPS-pentacene/CuPc bi-layer devices, the different conduction path not only reduced the total number of traps but also enhanced the sensing spectrum. It was found that, though the TIPS-pentacene was able to sense only blue and green colour well, and CuPc was able to sense only red and green colour well; the TIPS-pentacene/CuPc bi-layer were able to sense all three colors, enhancing the range of sensing. On illumination, bi-layer TIPS-pentacene/CuPc OFETs exhibited higher values of shift in threshold voltage (|ΔVTH|) compared to neat TIPS-pentacene and bare CuPc OFETs, due to change in the spatial distribution in the trap state density and associated pattern of trapping of photo-generated charge carriers. It was also found that the values of photo-responsivity (Rmax) and photo-detection time for the bi-layer OFETs were in between that for OFETs with TIPS-pentacene or CuPc.

Physics behind the improvement in breakdown voltage of AlGaN/GaN HEMTs with carbon-doping of GaN buffer is discussed. Modeling of carbon as acceptor traps and self-compensating acceptor/donor traps is discussed with respect to their impact on avalanche breakdown. Impact of carbon behaving as a donor as well as acceptor traps on electric field relaxation and avalanche generation is discussed in detail to establish the true nature of carbon in GaN that delays the avalanche action. This understanding of the behavior of carbon-doping in GaN buffer is then utilized to discuss design parameters related to carbon doped buffer. Design parameters such as undoped channel thickness and relative trap concentration induced by carbon-doping are discussed with respect to the performance metrics of breakdown voltage, leakage current, sheet charge density, and dynamic ON-resistance.

In part I of this paper, we developed physical insights into the role and impact of acceptor and donor traps—resulting from C-doping in GaN buffer—on avalanche breakdown in AlGaN/GaN HEMT devices. It was found that the donor traps are mandatory to explain the breakdown voltage improvement. In this paper, silicon doping is proposed and explored as an alternative to independently engineer donor trap concentration and profile. Keeping in mind the acceptor and donor trap relative concentration requirement for achieving higher breakdown buffer, as depicted in part I of this paper, silicon & carbon codoping of GaN buffer is proposed and explored in this paper. The proposed improvement in breakdown voltage is supported by physical insight into the avalanche phenomena and role of acceptor/donor traps. GaN buffer design parameters and their impact on breakdown voltage as well as leakage current are presented. Finally, a modified Si-doping profile in the GaN buffer is proposed to lower the C-doping concentration near GaN channel to mitigate the adverse effects of acceptor traps in GaN buffer.

Lowering the processing temperature is a crucial factor in the development of flexible electronic devices. Here we report the fabrication of high-performance OFETs based on room temperature deposited Ba0.5Sr0.5TiO3 (BST) as a high-k dielectric layer. The fabricated devices exhibited excellent performance while operating at a low voltage of -3 V along with demonstrating high operational stability when tested for 1 h bias stress and continuous transfer measurement cycles. In addition, inverter circuit performance is also investigated with these devices by connecting them to external loads.

The Gram-negative (−) bacterium Helicobacter pylori colonizes in the mucus gel layer above the gastric epithelium and has been considered to be a major etiologic factor in several gastric health complications including peptic ulcers, gastric MALT, gastritis, and gastric cancer in approximately 50% of the world’s population. Besides inducing colon carcinogenesis, the bacterium shows to be associated with different extragastric disorders. Eradication of H. pylori is reported to reduce 33–47% of gastric cancer; however, treatment of H. pylori against colon cancer is less effective in older people. Several targets of H. pylori to induce colorectal carcinogenesis have been hypothesized, and an association of gastric H. pylori with colorectal adenomatous polyps (CAPs) has been experimentally revealed. CAPs are precancerous lesions of epithelial cells and lead to colorectal cancer (CRC) from the adenomatous stage. Pathway analysis decrypts the cascade mechanism of CAPs via inducing matrix metalloproteinase (MMP), prostaglandin-endoperoxide synthase, and mucin with other molecular targets. Several therapeutic approaches have been established to eradicate H. pylori before inoculation and during histologic progression in early stages. This book chapter explains the impact and molecular mechanism of H. pylori in colon carcinogenesis and methods of therapeutic approaches.

The use of natural material components in organic devices increases nature friendliness and biodegradability. In this paper, water-soluble natural protein gelatin is explored as a gate dielectric for demonstration of high performance and low voltage (−3 V) operation in flexible organic field-effect transistors (OFETs). The fabricated p-channel devices showed excellent electrical characteristics of maximum field-effect mobility up to 3.0 cm2 V−1 s−1, high current on/off ratios, low subthreshold swing, and nearly zero threshold voltage due to the high-quality dielectric semiconductor interface achieved through optimized processes of fabricating flexible OFET devices. These devices exhibited very high operational stability as confirmed by various stability tests including bias-stress, repeatability, electromechanical stability, cyclic stability, and long-term ambient stability. For electromechanical stability, no significant changes in the performance were observed upon application of compressive and tensile strain due to bending. A very high environmental stability with almost unchanged electrical characteristics over 24 weeks was demonstrated. Further, circuit applicability was analyzed by switching characteristics from resistive load inverters. These results indicate gelatin as a promising biodegradable dielectric candidate for low voltage flexible OFETs.

Enterococci, the opportunistic pathogens, pose several serious and life-threatening infections such as urinary tract infections, sepsis, and endocarditis. The situation is worsening due to the development of drug resistance in these pathogens against several antibiotics. The addition of anti-enterococcal compounds with antioxidant activity in fermented and packaged food may help prevent the transmission of food-borne enterococcal infections. Scientists are in continuous search of such compounds from various sources. Hence, the present study has tested the diethyl ether extracts of thermophilic cyanobacteria, selected based on a previous study, against the multidrug-resistant and -sensitive strains of Enterococcus faecium. Out of the eleven tested extracts, 72% have shown anti-enterococcal activity against both strains. Among the extracts with anti-enterococcal activity, the diethyl ether extract of Leptolyngbya sp. (DEEL-3) inhibited the growth of VRE in a dose-dependent manner with a minimum inhibitory concentration of 2.0 mg mL-1. The DEEL-3 has also shown its antioxidant potential in terms of DPPH scavenging with an IC50 of 3.16 mg mL-1. The organism was named Leptolyngbya sp. HNBGU 003 based on 16SrRNA sequence homology analysis and morphological features. Further, the GC–MS analysis of the DEEL-3 has revealed the predominance of two phenolic compounds, phenol, 2,4-bis(1,1-dimethylethyl)-, phosphite (3:1) and tris(2,4-di-tert-butylphenyl) phosphate, in it. Thus, the anti-enterococcal and antioxidant activity of DEEL-3 may be attributed to these phenolics, which may be isolated and developed as food additives.

Performance of symmetric lateral doping-free bipolar junction transistor (BJT) on silicon on insulator (SOI) in universal gates and ring oscillator were investigated. Charge carriers in SOI at emitter and collector regions are induced with two unique approaches, i.e., the charge plasma (CP) and polarity control (PC). Four types of devices (CP-NPN, CP-PNP, PC-NPN, and PC-PNP) was used for bipolar CMOS type NAND and NOR gates. Excellent transient response with rise and fall time less than 5 ns and propagation delay less than 2.4 ns were obtained.

Flexible devices have been in focus for their applications in wearable electronics, displays, sensors, and memory. $\mathrm{PVP}/\mathrm{HfO}_{\mathrm{x}}$ based hybrid resistive random access memory devices were demonstrated on flexible PET substrates to study their resistive switching characteristics and memory application. These RRAM devices exhibited decent repeatability of more than 100 cycles with excellent $I_{\mathrm{o}\mathrm{n}}/I_{\mathrm{off}}$ of ~106 at 0.2 V as read voltage. With retention time of more than 6000 s and reliable switching operation, the fabricated devices have potential to be embedded in flexible electronic applications. Moreover, conduction mechanism in devices was found to be ohmic at lower voltage levels in high resistance state (HRS) and space charge limited conduction at higher voltage levels, occurring mainly due to traps sites available in PVP and $\mathrm{HfO}_{\mathrm{x}}$ . The AFM image confirms the presence of pinholes at PVP surface which will eventually assist in filament formation.

In this paper, firstly, some recently explored promising materials and processes for resistive random access memory (ReRAM) devices with bipolar switching mechanism along with their performance are discussed. Further, resistive switching behaviour of TiO x /graphene oxide (GO):poly(4-vinylphenol) (PVP) based bilayer in ReRAM devices is demonstrated. It was found that bipolar resistive switching behaviour is significantly enhanced by embedding 2D material such as GO in the organic polymer acting as switching layer. ReRAM devices with Ag/PVP:GO/TiO x /fluorine doped tin oxide (FTO) structure exhibited high ON/OFF current ratio (>103), low voltage operation, and high retention time. Bipolar resistive switching from these engineered active layers will have great potential for future large area and sustainable electronics.

Hybrid CBRAM devices based on PVP/HfOx bilayer were investigated for their switching performance. A reliable and low voltage bipolar resistive switching operation was observed in these devices with repeatability of 300 cycles, Ion/Ioff of 80, set (Vset) and reset (Vreset) voltages of 1.03 V and −0.68 V, retention time of 7200 s, and switching endurance of >2000 cycles in devices with 2.5 wt% PVP concentration. Low device-to-device variation was observed with 10 devices tested showing nearly similar switching parameters. Weibull's distribution of Vset and Vreset voltages have indicated reliable switching performance in devices. The pinholes formation in PVP layer guides the confined growth and dissolution of Ag conductive filament (CF) in the bilayer structure resulting in a stable, reliable and low voltage switching operation. PVP film roughness and pinholes depth have shown downtrend with PVP concentration. During the set process, a CF formed across the electrodes constitutes of Ag atoms, due to pinholes assisted electro-migration of Ag ions. Whereas in the reset process, the diffused Ag+ ions migrate back towards top electrode due to the electrochemical and joule-heating assisted rupture of CF in the PVP/HfOx bilayer structure.

BiFeO3 thin films are deposited on FTO coated glass substrates using a simple sol-gel deposition technique, limiting thickness about 70 nm and Ag/BiFeO3/FTO RRAM devices are prepared. The devices showed low-voltage bipolar switching with the maximum Ion/Ioff ~ 450, and low set and reset voltages ~ 1.1 V and -1.5 V, respectively. The devices are stable against on-off cycles with ~ 104 s retention time without any significant degradation. The variations in the set and reset voltages are 0.4 V and 0.6 V, respectively. We found that ohmic and trap-controlled space charge limited conductions are responsible for low and high resistance states, respectively. The resistive switching mechanism is attributed to the formation and rupturing of the metal filament during the oxidation and reduction of Ag ions for the set and reset states., 15 Pages, 4 Figures, Submitted for publication in Journal of American Ceramic Society

The critical role of the mixing ratio of the semiconductor and polymer solutions on the performance and electro-mechanical stability of the flexible blend OFETs is investigated. An improvement in the OFET performance was observed with increasing fraction of polymer in the solution. The maximum field-effect mobility improved from 0.08 for neat TIPS-pentacene OFETs to 0.24, 0.25 and 0.57 cm2 V−1 s−1 for semiconductor:polymer blend OFETs with mixing ratio of 3:1, 1:1 and 1:3 respectively. Under stress conditions of VDS = VGS = −5 V for 1 h, the 1:3 blend devices outperformed other categories of devices with very small drain current decay of ∼2% and 11% and small threshold voltage shift of 0.05 V and 0.27 V before and after 1.27% (Rbend = 5 mm) tensile strain application respectively. These devices also exhibited superior reliability with least performance spread over 100 continuous transfer characteristics measurement cycles before and after application of strain.