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Cytokinins, a type of phytohormones that induce division of cytoplasm, have considerable value in agriculture due to their influences on several physiological processes of plants such as morphogenesis, development of chloroplast, seed dormancy, leaf senescence, etc. Previously, it was assumed that plants obtain cytokinin from the soil produced by microbes as these hormones were first discovered in soil-inhabiting bacteria i.e., Agrobacterium tumefaciens. Later, the cytokinin biosynthesis gene, i.e., ipt gene, has been reported in plants too. Though plants synthesize cytokinins, several studies have reported that the exogenous application of cytokinins has numerous beneficial effects including the acceleration of plant growth and boosting economic yield. Cyanobacteria may be employed in the soil not only as the source of cytokinins but also as the source of other plant growth-promoting metabolites. These organisms biosynthesize the cytokinins using the enzyme isopentenyl transferases (IPTs) in a fashion similar to the plants; however, there are few differences in the biosynthesis mechanism of cytokinins in cyanobacteria and plants. Cytokinins are important for the establishment of interaction between plants and cyanobacteria as evidenced by gene knockout experiments. These hormones are also helpful in alleviating the adverse effects of abiotic stresses on plant development. Cyanobacterial supplements in the field result in the induction of adventitious roots and shoots on petiolar as well as internodal segments. The leaf, root, and stem explants of certain plants exhibited successful regeneration when treated with cyanobacterial extract/cell suspension. These successful regeneration practices mark the way of cyanobacterial deployment in the field as a great move toward the goal of sustainable agriculture.

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.

In this report, we have demonstrated the optical non-volatile memory characteristics using CuPc OFET. The memory operation was comprehensively demonstrated with different programming conditions. It was found that the programming of CuPc OFET with an electric pulse at the gate terminal under UV-light photo-illumination compared to other programming conditions, could substantially increase the memory window due to massive charge trapping in the polymer electret layer, which causes shift in the device transfer characteristics from low-conduction state (“OFF state”, or logic 0) to high conduction state (“ON state”, or logic 1) at VGS = 0V. From device operation at −50V, a memory window of greater than 45V could be achieved by applying a programming voltage of +70 V at the gate terminal under UV-light photo-illumination. Moreover, it was completely erased by applying −100 V at the gate terminal in dark.

Atomic layer deposited AlO x based resistive random access memories were fabricated with a new multi-temperature deposition (MTD) scheme, where a 40 nm thick AlO x film was deposited with temperature-thickness sequence of 150 °C (10 nm)/80 °C (20 nm)/150 °C (10 nm). Electrical characteristics of thus fabricated devices demonstrate improved bipolar resistive switching behavior with lower set and reset voltages of 0.65 V and − 1.15 V respectively, decent repeatability of 75 cycles, reliable data retention upto 10 3 s, small variation of 0.29 V and 0.17 V in set and reset voltages respectively, and symmetric current-voltage curves. The conduction mechanism has been explained as ohmic and space charge limited conduction at lower and higher voltages respectively. Due to different deposition temperature, oxygen vacancy concentration was different in each layer of the MTD film, which led to formation of a conductive filament with nonhomogeneous strength and dimensions across the film. Localization of effective switching phenomenon in the region with weaker conductive filament yielded an improved performance with lower switching voltages in corresponding multi-temperature devices.

Effect of ultra-violet (UV) irradiation (λpeak = 365 nm) on the electrical characteristics of solution processed flexible TIPS-pentacene organic field-effect transistors (OFETs) has been investigated. Pristine TIPS-pentacene OFETs demonstrated average field-effect mobility of 0.1 cm2 V−1 s−1, with near zero threshold voltage and current on-off ratio of ∼104. On UV irradiation, OFETs displayed a joint photoconductive and photovoltaic effect due to photo-generated excitons. The maximum current modulation and photo-responsivity obtained from these OFETs were ∼500 and ∼43 mA/W respectively at an intensity of 1.8 mW/cm2 while operating at a low voltage of −5 V. On increasing the irradiation time, a positive shift in the threshold voltage was observed. At larger values of irradiation time, a roll-off in maximum drain current and mobility values were observed, which was attributed to slight deterioration in crystallinity due to prolonged UV exposure, as confirmed from X-ray diffraction studies. Similar trend was observed for mobility and threshold voltage values, when gate bias during UV irradiation was increased. In addition, transistors exhibited a repeatable dynamic response to periodic pulses of UV irradiation.

Photo-response of solution processed flexible TIPS-pentacene organic field-effect transistors is evaluated under illumination with visible light of red, green, and blue colors having minimum wavelengths of 620, 520, and 460 nm. For −10 V operation, pristine photo-OFETs exhibited average field-effect mobility of 0.11 cm $^{2}\text{V}^{-1}\text{s}^{-1}$ , near zero threshold voltage, and current ON–OFF ratio of ~105. These photo-OFETs exhibited prevalent photovoltaic characteristics with shift in the threshold voltage upon illumination, which was found to increase with rising intensity, illumination time, and gate bias during illumination. For low-voltage operation at −5 V, maximum current modulation of $4\times 10^{4}$ and 102, and photo-responsivity of 17 mA/W and 35 mA/W, respectively, were achieved for blue (intensity of 1.7 mW/cm2) and green (intensity of 0.4 mW/cm2) light illuminations. However, these photo-OFETs did not show significant response to red light. A fast dynamic response to periodic pulses of illumination was also observed. For a gate bias of +10 V and illumination time of 500 s, maximum current modulation of 105 was achieved for blue light illumination.

BiFe 0.99 Cr 0.01 O 3 thin film is deposited on FTO glass using sol-gel technique. The deposited film is used in Ag/ BiFe 0.99 Cr 0.01 O 3 /FTO configuration to understand its potential as RRAM device. The device showed forming free bipolar RRAM characteristics with Ion/Ioff~80. The device showed non-volatile behaviour by maintaining its LRS and HRS states for 104 s. The device exhibits excellent reproducibility up to 100 cycles and reliability of V set and V reset voltage is observed. The endurance characteristics for 200 cycles ensures the stability of the device, further, conduction mechanism is attributed to filament formation and switching mechanism is assigned to migration of silver ion inside the film.

In this work, we have explored the effect of TIPSpentacene: polystyrene (PS) blend on electrical performance and photo-response of solution processed organic field-effect transistors (OFETs). It was observed that though the blend OFETs show better electrical performance, the photo-responsivity (R) of neat TIPS-pentacene OFETs was significantly better. This study was performed for different color lights such as blue, red, and green, as well as for ultraviolet light (UV). R was highest for blue color (~2600 mA/W for neat, ~230 mA/W for blend), and smaller for other cases. Low R value in blend devices is attributed to less trapping of photo-generated charge carriers during photo-illumination compared to their neat counterparts.