With the motivation of realizing an all graphene-based circuit for low power, we present a reliable nonvolatile graphene memory device, single-layer graphene (SLG) ferroelectric field-effect transistor (FFET). We demonstrate that exfoliated single-layer graphene can be optically visible on a ferroelectric lead-zirconate-titanate (PZT) substrate and observe a large memory window that is nearly equivalent to the hysteresis of the PZT at low operating voltages in a graphene FFET. In comparison to exfoliated graphene, FFETs fabricated with chemical vapor deposited (CVD) graphene exhibit enhanced stability through a bi-stable current state operation with long retention time. In addition, we suggest that the trapping/de-trapping of charge carriers in the interface states is responsible for the anti-hysteresis behavior in graphene FFET on PZT.

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The unique density of states of graphene at the device level is probed via tunneling spectroscopy of macroscopic metal-oxide-graphene structures. Local conductance minima from electrons tunneling into the graphene Dirac point are observed in the dI/dV spectra of both the single-junction and dual-junction configurations. Nonequally-spaced Landau levels, including the hallmark n=0 level, are observed in the presence of a magnetic field. Linear energy-momentum dispersion near the Dirac point, as well as the Fermi velocity, is extracted from both experiments. Local potential fluctuations and interface defects significantly influence these fine physical features, leading to peak broadening and anomalies comparing to the results from the ultra sharp scanning tunneling microscope tip. This study provides important implications for potential tunneling-based graphene devices in the future.

Experimental studies of pristine graphene devices currently rely on the fact that the graphene crystallites can be visible under optical microscopes when the underlying substrate is engineered to exhibit high contrast. Here, we present that graphene can be visualized not only on a dielectric substrate but also on a crystalline Si surface of a silicon-on-insulator ͑SOI͒ wafer ͑SIMOX and Bonded͒ with thicknesses of Si ϳ70 nm and buried oxide ϳ140 nm, using monochromatic illumination. In addition, we have found that Raman spectroscopy shows similar features to standard graphene on SiO 2 substrates independent of the polarity of the Si surface. Finally, the Raman spectrum on SOI exhibits a higher intensity compared to that on bulk Si due to the interference enhancement effect of graphene on SOI. Thus, the usage of optical microscopy and Raman spectroscopy for detecting, locating, and characterizing graphene serves as a high throughput method to further study graphene on semiconductor systems and other substrates beyond SiO 2 / Si.

1979, 289 pp., £11.65) This book is very good for beginners because the subject matter is explained very clearly and there are plenty of exercises (with answers) to reinforce the text. The authors put their stress on the fundamental digital circuits employed in computers. Only in the last two chapters which deal with microcomputers and programming are the fundamentals brought together.The first chapter is introductory and the second is concerned with simple binary arithmetic. Basic Boolean algebra concepts are described in chapter three. Chapters four, five and six deal with logic gates, combinational logic networks using Karnaugh map thesis and application to simple encoders, multiplexors, adders and Read Only Memory. The authors make no reference to the electronic circuits which comprise the logic gates. Chapter seven is concerned with the different types of flip-flops and the application to simple counters and registers is described in chapter nine.A short treatment of BCD and ASCII codes and a chapter on signed arithmetic complete the main part of the book. Using the INTEL 8080 architecture and instruction set as the example, the microcomputer is brought together in chapter eleven (28 pages on assembler programming). Bearing in mind the short length of this section of the book, the authors accomplish their task well. An appendix contains the full INTEL 8080 instruction set.Basically, this book is a good introductory text although many will regard the approach from simple logic at the beginning through to programming at the end, as rather old-fashioned. The fairly slow pace of the first ten chapters indicates the target readership: first-year undergraduates, technicians and mature engineers who have not had the benefit of formal educations in digital technology.