Nonvolatile memory technologies in Si-based electronics date back to the 1990s. Ferroelectric field-effect transistor (FeFET) was one of the most promising devices replacing the conventional Flash memory facing physical scaling limitations at those times. A variant of charge storage memory referred to as Flash memory is widely used in consumer electronic products such as cell phones and music players while NAND Flash-based solid-state disks (SSDs) are increasingly displacing hard disk drives as the primary storage device in laptops, desktops, and even data centers. The integration limit of Flash memories is approaching, and many new types of memory to replace conventional Flash memories have been proposed. Emerging memory technologies promise new memories to store more data at less cost than the expensive-to-build silicon chips used by popular consumer gadgets including digital cameras, cell phones and portable music players. They are being investigated and lead to the future as potential alternatives to existing memories in future computing systems. Emerging nonvolatile memory technologies such as magnetic random-access memory (MRAM), spin-transfer torque random-access memory (STT-RAM), ferroelectric random-access memory (FeRAM), phase-change memory (PCM), and resistive random-access memory (RRAM) combine the speed of static random-access memory (SRAM), the density of dynamic random-access memory (DRAM), and the nonvolatility of Flash memory and so become very attractive as another possibility for future memory hierarchies. Many other new classes of emerging memory technologies such as transparent and plastic, three-dimensional (3-D), and quantum dot memory technologies have also gained tremendous popularity in recent years. Subsequently, not an exaggeration to say that computer memory could soon earn the ultimate commercial validation for commercial scale-up and production the cheap plastic knockoff. Therefore, this review is devoted to the rapidly developing new class of memory technologies and scaling of scientific procedures based on an investigation of recent progress in advanced Flash memory devices.

In the advancement of the semiconductor device technology, ZnO could be a prospective alternative than the other metal oxides for its versatility and huge applications in different aspects. In this review, a thorough overview on ZnO for the application of resistive switching memory (RRAM) devices has been conducted. Various efforts that have been made to investigate and modulate the switching characteristics of ZnO-based switching memory devices are discussed. The use of ZnO layer in different structure, the different types of filament formation, and the different types of switching including complementary switching are reported. By considering the huge interest of transparent devices, this review gives the concrete overview of the present status and prospects of transparent RRAM devices based on ZnO. ZnO-based RRAM can be used for flexible memory devices, which is also covered here. Another challenge in ZnO-based RRAM is that the realization of ultra-thin and low power devices. Nevertheless, ZnO not only offers decent memory properties but also has a unique potential to be used as multifunctional nonvolatile memory devices. The impact of electrode materials, metal doping, stack structures, transparency, and flexibility on resistive switching properties and switching parameters of ZnO-based resistive switching memory devices are briefly compared. This review also covers the different nanostructured-based emerging resistive switching memory devices for low power scalable devices. It may give a valuable insight on developing ZnO-based RRAM and also should encourage researchers to overcome the challenges.

Supercapacitor characteristics of manganese oxide/nickel <mml:math display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi mathvariant="normal">Mn</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Ni</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>(MnOx∕Ni) and manganese oxide/carbon nanotubes/nickel <mml:math display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi mathvariant="normal">Mn</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mo>∕</mml:mo><mml:mi>CNTs</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Ni</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>(MnOx∕CNTs∕Ni) nanocomposite electrodes were investigated in this study. The CNTs were deposited on the Ni substrate by electrophoresis in a <mml:math display="inline"><mml:mrow><mml:mn>0.5</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mg</mml:mi><mml:mspace width="0.3em"></mml:mspace><mml:mi>CNT</mml:mi><mml:mo>∕</mml:mo><mml:mn>1</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mL</mml:mi></mml:mrow></mml:math>0.5mgCNT∕1mL dimethylformamide solution, whereas the <mml:math display="inline"><mml:mrow><mml:mi mathvariant="normal">Mn</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mi>x</mml:mi></mml:msub></mml:mrow></mml:math>MnOx were synthesized by anodic deposition in a <mml:math display="inline"><mml:mrow><mml:mn>0.16</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">M</mml:mi></mml:mrow></mml:math>0.16M manganese sulfate pentahydrate aqueous solution on substrates. The crystallinity and surface morphology of these electrodes were determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The capacitive properties of these electrodes were demonstrated by cyclic voltammetry with scan rates ranging from <mml:math display="inline"><mml:mrow><mml:mn>5</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mtext>to</mml:mtext><mml:mspace width="0.3em"></mml:mspace><mml:mn>100</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mV</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">s</mml:mi></mml:mrow></mml:math>5to100mV∕s . The specific capacitances of the <mml:math display="inline"><mml:mrow><mml:mi mathvariant="normal">Mn</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mo>∕</mml:mo><mml:mi>CNT</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Ni</mml:mi></mml:mrow></mml:math>MnOx∕CNT∕Ni nanocomposite electrode were 415 and <mml:math display="inline"><mml:mrow><mml:mn>388</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">F</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">g</mml:mi></mml:mrow></mml:math>388F∕g with scan rates of 5 and <mml:math display="inline"><mml:mrow><mml:mn>100</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mV</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">s</mml:mi></mml:mrow></mml:math>100mV∕s , respectively. After <mml:math display="inline"><mml:mrow><mml:mn>1000</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mtext>cycles</mml:mtext></mml:mrow></mml:math>1000cycles of operation, this electrode can maintain 79% of its original capacitance. These <mml:math display="inline"><mml:mrow><mml:mi mathvariant="normal">Mn</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mo>∕</mml:mo><mml:mi>CNT</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Ni</mml:mi></mml:mrow></mml:math>MnOx∕CNT∕Ni nanocomposite electrodes possessing good electrochemical reversibility and high capacitance may be appropriate for supercapacitor application in the future.