Using high-quality polycrystalline chemical-vapordeposited diamond films with large grains (∼ 100 µm), field effect transistors (FETs) with gate lengths of 0.1 µm were fabricated. From the RF characteristics, the maximum transition frequency f T and the maximum frequency of oscillation f max were ∼ 45 and ∼ 120 GHz, respectively. The f T and f max values are much higher than the highest values for singlecrystalline diamond FETs. The dc characteristics of the FET showed a drain-current density I DS of 550 mA/mm at gate-source voltage V GS of −3.5 V and a maximum transconductance g m of 143 mS/mm at drain voltage V DS of −8 V. These results indicate that the high-quality polycrystalline diamond film, whose maximum size is 4 in at present, is a most promising substrate for diamond electronic devices.Index Terms-Field effect transistor (FET), hydrogen terminated, polycrystalline diamond, RF performance.

We compare the results of ab initio calculations with measured reflection anisotropy spectra and show that strongly bound surface-state excitons occur on the clean diamond (100) surface. These excitons are found to have a binding energy close to 1 eV, the strongest ever observed at a semiconductor surface. Important electron-hole interaction effects on the line shape of the optical transitions above the surface-state gap are also found.

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Ferroelectric random access memory (FeRAM) is an attractive candidate technology for embedded nonvolatile memory, especially in applications where low power and high program speed are important. Market introduction of high-density FeRAM is, however, lagging behind standard complementary metal-oxide semiconductor (CMOS) because of the difficult integration technology. This paper discusses the major integration issues for high-density FeRAM, based on SrBi2Ta2O9 (strontium bismuth tantalate or SBT), in relation to the fabrication of our stacked cell structure. We have worked in the previous years on the development of SBT-FeRAM integration technology, based on a so-called pseudo-three-dimensional (3D) cell, with a capacitor that can be scaled from quasi two-dimensional towards a true three-dimensional capacitor where the sidewalls will importantly contribute to the signal. In the first phase of our integration development, we integrated our FeRAM cell in a 0.35μm CMOS technology. In a second phase, then, possibility of scaling of our cell is demonstrated in 0.18μm technology. The excellent electrical and reliability properties of the small integrated ferroelectric capacitors prove the feasibility of the technology, while the verification of the potential 3D effect confirms the basic scaling potential of our concept beyond that of the single-mask capacitor. The paper outlines the different material and technological challenges, and working solutions are demonstrated. While some issues are specific to our own cell, many are applicable to different stacked FeRAM cell concepts, or will become more general concerns when more developments are moving into 3D structures.

Evans D A, Roberts O R, Vearey-Roberts A R, Langstaff D P, Twitchen D J and Schwitters M 2007 Direct observation of Schottky to ohmic transition in Al-diamond contacts using realtime photoelectron spectroscopy Appl. Phys. Lett. 91 132114 doi:10.1063/1.2790779Real-time photoelectron spectroscopy and in situ electrical measurements have been applied to the formation of Al contacts on p-type diamond. At 294 K, an initially uniform Al film induces band bending in the diamond consistent with the measured (current-voltage) barrier height of 1.05 V. The temperature-induced transition to an Ohmic contact has been monitored in real time revealing a direct correlation between the onset of surface bonding at 755 K and an abrupt change in surface band bending. The reaction temperature is lower than previously believed, and there is a second transition point at 1020 K where the rates of change of both reaction and band bending increase sharply.authorsversionPeer reviewe