Thin films of Er doped AlN, ∼ 200 nm thick, were grown on indium tin oxide/aluminum titanium oxide/glass substrates using RF magnetron sputtering in a pure nitrogen atmosphere. To optically activate Er all films were subject to post-deposition annealing in flowing nitrogen atmosphere at atmospheric pressure at temperatures between 1023-1223 K for 10-60 minutes. The visible cathodoluminescence (CL) in the green was detected at both 11 K and 300K. The strongest CL peaks were observed at 558 nm and 537 nm (11 K), which correspond to the transitions from 4S3/2 and 2H11/2 to the 4I15/2 ground level. Electroluminescence (EL) studies of AlN:Er alternating-current thin-film electroluminescent (ACTFEL) devices were performed at 300 K. The turn-on voltage was found to be around 80-100 V for our ACTFEL devices. The intensity of the EL emission rapidly increases with the voltage increasing in the investigated range of 110-130 V.

Ga2O3:Mn and (Ga2O3-SnO2):Eu thin films have been prepared by a sol-gel process. High luminance emissions were obtained in TFEL devices: green using a Ga2O3:Mn and red using a Ga2O3:Eu or a SnO2:Eu thin-film emitting layer. These sol-gel prepared devices were produced without using any vacuum processes and always exhibited higher luminances than equivalent devices prepared by r.f. magnetron sputtering: 40, 309 and above 1000 cd/m2 using SnO2:Eu, Ga2O3:Eu and Ga2O3:Mn phosphor thin films, respectively, in TFEL devices prepared by the sol-gel process and driven at 1kHz.

We report the oxide charging effects on metal oxide semiconductor (MOS) structure caused by PH3/He ion shower doping. The parallel negative shift of flat-band voltage occurred for the ion-doped PETEOS samples even after thermal annealing. When the ion dose was higher, this shift was larger. These results show that a considerable amount of positive charges were induced inside the oxide films after PH3/He ion shower doping process. For the same ion dose, the flat-band voltage shift is larger when the thickness of PETEOS is thicker. When the ion dose was 1.5×1017cm−2 and the thickness of PETEOS was 80nm, the shift of flat-band voltage was larger than −7V. We can conclude that PH3/He ion shower doping process induces the positive charges, which result in the flat band voltage shift of MOS capacitors, in the bulk oxide films when oxide films are exposed to ion shower doping.

Synthesis of multi-wall carbon nanotubes (MWNTs) was attempted by microwave plasma enhanced chemical vapor deposition using CH4/H2/NH3 gases on Ni/Cr-coated glass at low temperature. The synthesis was investigated by optical emission spectroscopy and quadrupole mass spectroscopy. It was observed that MWNTs could be grown within a very restrictive range of gas compositions. An addition of a small amount of NH3 resulted in a decrease of C2H2, which can be used to estimate the amount of carbon sources in plasma for the growth of MWNTs, and an increase of CN and Hα radicals acting as etching species of carbon phases. These results show that carbon nanotubes can be grown only under an appropriate condition that the growing process surpasses the etching process. The optimum C2H2 /Hα ratio in a gas mixture was found to be between 1 and 3 for the MWNT growth at low temperature.

For enhancement and stabilization of electron emission, Mo and Co silicides were formed from Mo mono-layer and Ti/Co bi-layers on single crystal silicon FEAs, respectively. Using the slope of Fowler-Nordheim curve and tip radius measured from SEM, the effective work function of Mo and Co silicide FEAs are calculated to be 3.13 eV and 2.56 eV, respectively. Compared with silicon field emitters, Mo and Co silicide exhibited 10 and 34 times higher maximum emission current, 10 V and 46 V higher failure voltage, and 6.1 and 4.8 times lower current fluctuation, respectively. Moreover, the emission currents of the silicide FEAs depending on vacuum level are almost same in the range of 10−9 ∼ 10−6 torr. This result shows that silicide is robust in terms of anode current degradation due to the absorption of air molecules.

The electronic structure of nanodiamond clusters containing between 34 and 913 carbon atoms was calculated using a tight-binding Hamiltonian. All clusters had shapes represented by an octahedron with (111) facets with the top and the bottom vertices truncated to introduce (100) surfaces. The tight-binding Hamiltonian consisted of environment-dependent matrix elements, and C-H parameters fit to reproduce energy states of the cyclic C6 and methane. The calculations predict a density of states similar to bulk diamond for clusters with radii greater than ∼2.5nm, and insignificant differences in the potential distribution between the clusters and bulk diamond for radii greater than ∼1nm. Hydrogen passivated nanodiamond clusters are estimated to have an electron affinity of approximately -1.8 eV.

Electrical characteristics of Spindt-type Molybdenum (Mo) field emitter triode devices with varied emitter tip-height have been studied based on device modeling and experiment. Potential and electric field distributions with varied the emitter tip-height has been simulated. It is observed that the electric field of the top of the higher emitter tip was strongly affected with the anode-gate distance and the anode voltage compared to conventional field emitter triode device. Experimental results with varied different tip-height were in good agreement with that of calculated results. We present the possibility of “depletion mode” field emitter triode device.

Large grains in thin silicon films were grown by controlling the location of unmolten islands, which are left after near-complete melting of the film during excimer laser crystallization. As the initially amorphous film was first transformed in small grain polycrystalline silicon, these islands contain seeds for crystal growth. To get a single large grain, either the number of seeds was reduced to one or a single one was selected from the seeds by a ‘grain filter’. Former was achieved by making a small indentation in the isolating layer underlying the silicon film so that seeds remain embedded in the indentation. Latter was achieved by making a small diameter hole in the underlying isolating layer, which was filled with amorphous silicon. The lateral growth is preceded by a vertical growth phase during which a single grain is filtered from the initial set of seeds present at the bottom of the hole. In the experiment described, highest yield was achieved for samples in which the melt-depth to hole- diameter ratio was largest.

Electron field emission from diamond, diamond-like carbon, carbon nanotubes and nanostructured carbon is compared. It is found that in all practical cases that emission occurs from regions of positive electron affinity with a barrier of ∼5 eV and with considerable field enhancement. The field enhancement in nanotubes arises from their geometry. In diamond, the field enhancement occurs by depletion of grain boundary states. In diamond-like carbon we propose that it occurs by the presence of sp2-rich channels formed by the soft conditioning process.

For the development of new electron-emissive materials knowledge of the work function Φ and changes in Φ is of particular interest. Among the various methods, the ultra-high vacuum (UHV) compatible scanning Kelvin Probe has been proven to be a superior technique to measure work function changes due to e.g. UHV cleaning processes, chemical contamination, thermal processing etc. with high accuracy (<1meV).

The Kelvin Probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (Φtip) is unknown.

Here, we present a novel approach to measure Φtip with the Kelvin Probe via the photoelectric effect, where a Gd foil is used as the photoelectron source. This method thus provides the true work function of the sample surface with an accuracy of approx. 50meV. We demonstrate the application of the technique by in situ work function measurements on evaporated layers of the low work function material LaB6 on a Re substrate and follow the changes in Φ of LaB6 due to the surface adsorption of residual gas molecules. Thus, the extended Kelvin Probe method provides an excellent tool to characterise and monitor the stability of low work function surfaces.

Imaging of field emission and photoemission from diamond surfaces is accomplished with a high resolution photo-electron emission microscope (PEEM). Measurements obtained as a function of sample temperature up to 1000°C display thermionic field emission images (TFEEM). The system can also record the emission current versus applied voltage. N-doped diamond films have been produced by MPCVD with a N/C gas phase ratio of 48. The surfaces display uniform emission in PEEM at all temperatures. No FEEM images are detectable below 500°C. At ∼680°C the T-FEEM and PEEM images are nearly identical in intensity and uniformity. This is to be contrasted with other carbon based cold cathodes in which the emission is observed from only a low density of highly emitting sites. The I/V measurements obtained from the N-doped films in the T-FEEM configuration show a component that depends linearly on voltage at low fields. At higher fields, an approximately exponential dependence is observed. At low temperatures employed (<700°C), the results indicate a thermionic component to the emitted current.

We have grown vertically aligned carbon nanotubes on a large area of Co-Ni codeposited Si substrates by thermal chemical vapor deposition using C2H2 gas. The carbon nanotubes grown by the thermal chemical vapor deposition are multi-wall structure, and the wall surface of nanotubes is covered with defective graphite sheets or carbonaceous particles. The carbon nanotubes range from 50 to 120 nm in diameter and about 130 μm in length at 950 °C. Steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically. The turn-on voltage was about 0.8 V/μm with a current density of 0.1 μA/cm2 and emission current reveals the Fowler-Nordheim mode.

We analyze a non-traditional version of semiconductor field emission structure, based on silicon cones arrays and destined for application in low-voltage vacuum microelectronics devices. In proposed construction, the gate electrode is used as Shottky-barrier contact on silicon tips. Due to Shottkybarrier contact we have obtained depletion layer in tip body under the gate electrode. Therefore variation of the gate electric potential provides the emitter current modulation. Experimental structures were fabricated with about 28000 silicon cones per 1 mm2 by reactive ion etching through a silica mask. Using a quasi two-dimensional model, we have computed these emitter structures. The model takes into account non-uniformity of silicon cone cross-section. Here, we study the influence of emitter tips parameters on the structure performance. Initial results prove the possibility of cathode current electric control with the gate electrode potential. Additionally we have obtained some other electric parameters of the emitter with the Shottky-barrier contact. The results of numerical analysis and experimental study provide a guide for design of proposed field emitter structure.

Polysilicon is a promising candidate material for field-emission microelectronics devices. It can be competitive for large-size, cost-sensitive applications such as flat-panel displays and micro electro-mechanical systems. Singly-addressable arrays of field-emission cells were fabricated in a matrix configuration using a subtractive process on Polysilicon-On-Insulator substrates. Matrix rows were fabricated as insulated polycrystalline silicon strips with sharp emission tips; and matrix columns were deposited as gold thin film electrodes with round gate openings. Ion implantation has been used to provide the required conductivity of the poly-Si layer. To reduce radius of curvature of the polysilicon tips, a sharpening oxidation process was used. The final device had polysilicon emission tips with end radii smaller than 15 nm, surrounded by gate apertures of 0.4 μm in diameter. Field emission properties of the cathodes were measured at a pressure of about 10-8 Torr, to emulate vacuum conditions available in sealed vacuum microelectronics devices. It was found that an emission current of 1 nA appears at a gate voltage of 25 V and can be increased up to 1μA at 70 V. Over this range of current, no “semiconductor” deviation from the Fowler-Nordheim equation was observed. I-V characteristics measured in cells of a 10x10 matrix, with a cell spacing of 50 μm demonstrated good uniformity and reproducibility.

Solid-phase crystallization (SPC) behavior of a-Si film [a-Si(II)] in which oxygen concentration (CO) is higher at the a-Si/SiO2 interface (CO=5×1021/cm3) than at the film surface (CO=3×1020/cm3) has been investigated. The results were also compared with that of a-Si single layer [a- Si(I), 600 Å] with CO=3×1020/cm3. It has been found that the interface-nucleation was suppressed in the a-Si(II) and the surface-nucleation occurred to make a poly-Si/a-Si (300 Å/300Å) bilayer structure. Many equiaxial grains with sizes of 1∼2 [.proportional]m were formed in the surface- nucleated poly-Si layer. Compared with the results of conventional SPC poly-Si (600 Åthick) in which elliptical grains with sizes of 0.5∼1 [.proportional]m were formed by the interface (a-Si/SiO2)- nucleation, we concluded that the poly-Si/a-Si bilayer scheme is a method to improve the microstructure of SPC poly-Si film.

In this paper, we propose concentric circular lateral field emitter structure which is more sstable in fabricating and maintaining vacuum conditions. The new FEAs have concentric circular shape while our previous FEAs are stripe type. The anode is formed at inner circle and the cathode is outer circle respectively. We use Molybdenum or Silicon dioxide as a sealing material. After we fabricating tips, Molybdenum or Silicon dioxide is deposited with e-beam evaporator at base pressure of 3.5×10−6Torr. In this process, the micro-cavity remains vacuum cavity without filling Molybdenum or oxide due to step coverage of evaporation. It should be noted that the vacuum level of the micro-cavity can be identical to the base pressure of the e-gun evaporator chamber. All of the two types of new FEAs show good reproducibility in fabricating and maintaining vacuum conditions. Field emitter structure that the anode is located at inner circle shows superior field emission characteristics. The measurements of long term stability for the anode current show that oxide is the most promising material for in-situ vacuum sealing.

The influence of hydrogen in a precursor on excimer laser crystallization behavior was investigated. The crystal orientation and lattice constant of polycrystalline silicon films were analyzed by X-ray diffraction measurement. An intensity ratio of 111 to 220 was used as an index of the (111) preferred orientation. A randomly oriented film with an index of 2 at lower energy density changed to the highly (111) oriented phase with an index of more than 15 at higher energy density. It was observed in the PE-CVD films that increasing the hydrogen in the precursor films decreased the orientation index. The lattice constant of the laser-annealed PE-CVD silicon was found to be larger than that of the PVD silicon and to decrease with an increase in laser energy density. The network structure of as-deposited PVD film with less hydrogen content was denser than that of as-deposited PE-CVD. The network structure of the precursor strongly affected the crystal growth, and the structure of the ELC poly-Si was still affected by the precursors, even though the hydrogen content decreased after laser annealing.

Ce3+ luminescence in Ce-activated yttrium aluminium borates was studied. Photoluminescnece was excited by continuous-wave UV or by pulse laser irradiation. Cathodoluminescence was excited at the acceleration voltage in the range 5 to 600 V. These phosphors show under continuous wave UV excitation three emission peaks: in near UV, deep blue and light blue ranges. The light blue peak at around 490 nm which may be connected to forbidden 2D3/2 → 2F7/2 transition appears in continuous wave-excited photoluminescence only and does not appear in cathodoluminescence nor under pulse excitation. The blue-emitting Ce- activated yttrium aluminium borates exhibit unusually strong activator ion-host lattice interaction. As a result a substantial red shift in the emission is induced by Ce concentration increase and complicated concentration dependence of the emission intensity is observed.

Field-emitter arrays (FEAs) are desirable for use as electron emitters in microwave-tube amplifiers because they can provide such advantages as higher efficiency and faster turn-on compared to their thermionic counterparts. Calculations have shown that Spindt-type metal and semiconductor emitters operate well below intrinsic current limits due to thermal effects, even for high-current applications such as klystrodes, twystrodes, and traveling-wave amplifiers. Nevertheless, the primary barrier to FEA utilization in such applications is premature failure due to arcing. These failures appear to be produced by ionization of gas molecules and/or desorbed contaminants, which are exacerbated by a poor vacuum environment. Lifetime and stability issues have been largely resolved for less stringent applications, such as flat-panel displays, through the use of integrated passive resistors that provide current limiting. However, such an approach is not directly compatible with operation at high frequency and current density. Other more complex approaches, such as the incorporation of active control in the form of integrated transistors, have also been demonstrated, but again, only for FEAs used in displays. This paper will review some of these schemes in the context of their efficacy in improving lifetime and stability of FEA cold cathodes in high-frequency applications. A theoretical analysis will be given of the effect on highfrequency performance of incorporating arc protection structures into Spindt-type metal FEAs. Specifically, two approaches will be considered: passive protection schemes such as the use of a modified thin film resistive layer, and active schemes such as FETs and saturated current limiters.

The comparison of TFTs fabricated on films processed by conventional excimer laser an- nealing (ELA) and sequential lateral solidification (SLS) demonstrates the dependence of the device characteristics on the microstructure of the device channel region. We report the perform- ance characteristics of non-self-aligned coplanar n- and p-channel low temperature TFTs fabricated on 1000-Å-thick films on Corning 1737 glass substrates that were directionally solidified using SLS. The devices were aligned so that the grain boundaries were parallel to the direction of the source-drain current flow. These results were compared with those obtained from devices fabricated on conventional ELA-processed polycrystalline Si films (with average grain size of ∼3000 Å) with identical methods. The values for channel mobility obtained from the SLS TFTs are ∼370 cm2/Vsec for n-channel and ∼140 cm2/Vsec for p-channel devices, compared to ∼100 and ∼60 respectively for ELA TFTs. Other device characteristics of SLS TFTs were Ion/Ioff > 107 at Vd=0.1V, and subthreshold slopes less than 0.5V/dec. We further discuss the physical implications of the results and present additional details of the devices.