bluuebunny/crossref_metadata_2025 huggingface dataset:
Metalorganic molecular-beam epitaxy and characterization of GaAsNSe/GaAs superlattices emitting around 1.5-μm-wavelength region
Authors: Uesugi K. , Suemune I. , Machida H. , Shimoyama N.
Published: February 2003

GaAsNSe/GaAs superlattices (SLs) were grown on GaAs(001) substrates by metalorganic molecular-beam epitaxy. Strong photoluminesence (PL) emission around the 1.5-μm-wavelength region was observed from these SLs without thermal annealing, which suggests that high electron concentrations in GaAsNSe layers increase the radiative recombination rate, making the nonradiative recombination relatively unimportant. It is also demonstrated that (GaAsNSe/GaAs SLs)/(GaAsN/GaAsSb SLs)/GaAs heterostructures are effective to reduce the strain accumulation in the layers, which will also form effective separated confinement heterostructure. The temperature dependence of the PL peak intensity is drastically improved by combining the GaAsN/GaAsSb SLs with the GaAsNSe/GaAs SLs following this scheme. The PL peak intensity observed at 300 K was as large as 20% of that observed at 19 K. This improvement of the optical property will be attributed to the elimination of nonradiative defects by minimizing average strain in the samples.
Acoustic detection of microbubble formation induced by enhanced optical breakdown of silver/dendrimer nanocomposites
Authors: Milas Susanne M. , Ye Jing Yong , Norris Theodore B. , Balogh Lajos P. , Baker James R. , Hollman Kyle W. , Emelianov Stanislav , O’Donnell Matthew
Published: February 2003

We utilize a real-time acoustic technique, based on pulse-echo measurements to detect formation of microbubbles in an aqueous solution of a silver/dendrimer nanocomposite (DNC). Wave-field plots of successive recordings illustrate the generation and behavior of bubbles created by the optical breakdown process. A significant threshold reduction is achieved with DNC particles compared to its host dendrimer, enabling a diverse field of low-threshold breakdown applications.
Free energy barrier to melting of single-chain polymer crystallite
Authors: Hu Wenbing , Frenkel Daan , Mathot Vincent B. F.
Published: February 2003

We report Monte Carlo simulations of the melting of a single-polymer crystallite. We find that, unlike most atomic and molecular crystals, such crystallites can be heated appreciably above their melting temperature before they transform to the disordered “coil” state. The surface of the superheated crystallite is found to be disordered. The thickness of the disordered layer increases with super-heating. However, the order–disorder transition is not gradual but sudden. Free-energy calculations reveal the presence of a large free-energy barrier to melting.
Lower bounds for the total stopping time of 3𝑥+1 iterates
Authors: Applegate David , Lagarias Jeffrey
Published: February 2003

The total stopping time

σ

∞

(
n
)

\sigma _{\infty }(n)

of a positive integer

n
n

is the minimal number of iterates of the

3
x
+
1

3x+1

function needed to reach the value

1
1

, and is

+
∞

+\infty

if no iterate of

n
n

reaches

1
1

. It is shown that there are infinitely many positive integers

n
n

having a finite total stopping time

σ

∞

(
n
)

\sigma _{\infty }(n)

such that

σ

∞

(
n
)
>
6.14316
log
⁡
n
.

\sigma _{\infty }(n) > 6.14316 \log n.

The proof involves a search of

3
x
+
1

3x +1

trees to depth 60, A heuristic argument suggests that for any constant

γ
>

γ

B
P

≈
41.677647

\gamma > \gamma _{BP} \approx 41.677647

, a search of all

3
x
+
1

3x +1

trees to sufficient depth could produce a proof that there are infinitely many

n
n

such that

σ

∞

(
n
)
>
γ
log
⁡
n
.

\sigma _{\infty }(n)>\gamma \log n.

It would require a very large computation to search

3
x
+
1

3x + 1

trees to a sufficient depth to produce a proof that the expected behavior of a “random”

3
x
+
1

3x +1

iterate, which is

γ
=

2

log
⁡
4

/

3

≈
6.95212
,

\gamma =\frac {2}{\log 4/3} \approx 6.95212,

occurs infinitely often.
Mixed finite volume methods on nonstaggered quadrilateral grids for elliptic problems
Authors: Chou So-Hsiang , Kwak Do , Kim Kwang
Published: February 2003

We construct and analyze a mixed finite volume method on quadrilateral grids for elliptic problems written as a system of two first order PDEs in the state variable (e.g., pressure) and its flux (e.g., Darcy velocity). An important point is that no staggered grids or covolumes are used to stabilize the system. Only a single primary grid system is adopted, and the degrees of freedom are imposed on the interfaces. The approximate flux is sought in the lowest-order Raviart–Thomas space and the pressure field in the rotated-Q1Q1nonconforming space. Furthermore, we demonstrate that the present finite volume method can be interpreted as a rotated-Q1Q1nonconforming finite element method for the pressure with a simple local recovery of flux. Numerical results are presented for a variety of problems which confirm the usefulness and effectiveness of the method.
Class numbers of real cyclotomic fields of prime conductor
Authors: Schoof René
Published: February 2003

The class numbers

h

l

+

h_{l}^{+}

of the real cyclotomic fields

Q

(

ζ

l

+

ζ

l

−
1

)

\mathbf {Q}(\zeta _{l}^{}+\zeta _{l}^{-1})

are notoriously hard to compute. Indeed, the number

h

l

+

h_{l}^{+}

is not known for a single prime

l
≥
71

l\ge 71

. In this paper we present a table of the orders of certain subgroups of the class groups of the real cyclotomic fields

Q

(

ζ

l

+

ζ

l

−
1

)

\mathbf {Q}(\zeta _{l}^{}+\zeta _{l}^{-1})

for the primes

l
>
10
,
000

l>10,000

. It is quite likely that these subgroups are in fact equal to the class groups themselves, but there is at present no hope of proving this rigorously. In the last section of the paper we argue —on the basis of the Cohen-Lenstra heuristics— that the probability that our table is actually a table of class numbers

h

l

+

h_{l}^{+}

, is at least

98
98%

.
The first known type (7,1) amicable pair
Authors: Garcia Mariano
Published: February 2003

Amicable pairs of type

(
i
,
1
)

(i, 1)

have been the object of special search partly because they breed other amicable pairs. Examples exist for

i
=
2
,
3
,
4
,
5
,

i=2, 3, 4, 5,

and 6. In this paper we exhibit the first known type

(
7
,
1
)

(7,1)

pair.
Linear quintuple-product identities
Authors: Blecksmith Richard , Brillhart John
Published: February 2003

In the first part of this paper, series and product representations of four single-variable triple products

T
0

T_0

,

T
1

T_1

,

T
2

T_2

,

T
3

T_3

and four single-variable quintuple products

Q
0

Q_0

,

Q
1

Q_1

,

Q
2

Q_2

,

Q
3

Q_3

are defined. Reduced forms and reduction formulas for these eight functions are given, along with formulas which connect them. The second part of the paper contains a systematic computer search for linear trinomial

Q
Q

identities. The complete set of such families is found to consist of two 2-parameter families, which are proved using the formulas in the first part of the paper.
Maximum norm stability of difference schemes for parabolic equations on overset nonmatching space-time grids
Authors: Mathew T. , Russo G.
Published: February 2003

In this paper, theoretical results are described on the maximum norm stability and accuracy of finite difference discretizations of parabolic equations on overset nonmatching space-time grids. We consider parabolic equations containing a linear reaction term on a space-time domain

Ω
×
[
0
,
T
]

\Omega \times [0,T]

which is decomposed into an overlapping collection of cylindrical subregions of the form

Ω

l

∗

×
[
0
,
T
]

\Omega _{l}^{\ast } \times [0,T]

, for

l
=
1
,
…
,
p

l=1, \dotsc , p

. Each of the space-time domains

Ω

l

∗

×
[
0
,
T
]

\Omega _{l}^{\ast } \times [0,T]

are assumed to be independently grided (in parallel) according to the local geometry and space-time regularity of the solution, yielding space-time grids with mesh parameters

h

l

h_{l}

and

τ

l

\tau _{l}

. In particular, the different space-time grids need not match on the regions of overlap, and the time steps

τ

l

\tau _{l}

can differ from one grid to the next. We discretize the parabolic equation on each local grid by employing an explicit or implicit

θ
\theta

-scheme in time and a finite difference scheme in space satisfying a discrete maximum principle. The local discretizations are coupled together, without the use of Lagrange multipliers, by requiring the boundary values on each space-time grid to match a suitable interpolation of the solution on adjacent grids. The resulting global discretization yields a large system of coupled equations which can be solved by a parallel Schwarz iterative procedure requiring some communication between adjacent subregions. Our analysis employs a contraction mapping argument. Applications of the results are briefly indicated for reaction-diffusion equations with contractive terms and heterogeneous hyperbolic-parabolic approximations of parabolic equations.
Relative invariants of some 2-simple prehomogeneous vector spaces
Authors: Kogiso Takeyoshi , Miyabe Go , Kobayashi Miyuki , Kimura Tatsuo
Published: February 2003

In this paper, we shall construct explicitly irreducible relative invariants of two 2-simple prehomogeneous vector spaces. Together with a preprint by the same authors, this completes the list of all relative invariants of regular 2-simple prehomogeneous vector spaces of type I.
About the sharpness of the stability estimates in the Kreiss matrix theorem
Authors: Spijker M. , Tracogna S. , Welfert B.
Published: February 2003

One of the conditions in the Kreiss matrix theorem involves the resolvent of the matrices

A
A

under consideration. This so-called resolvent condition is known to imply, for all

n
≥
1

n\ge 1

, the upper bounds

‖

A
n

‖
≤
e
K
(
N
+
1
)

\|A^n\|\le eK(N+1)

and

‖

A
n

‖
≤
e
K
(
n
+
1
)

\|A^n\|\le eK(n+1)

. Here

‖
⋅
‖

\|\cdot \|

is the spectral norm,

K
K

is the constant occurring in the resolvent condition, and the order of

A
A

is equal to

N
+
1
≥
1

N+1\ge 1

. It is a long-standing problem whether these upper bounds can be sharpened, for all fixed

K
>
1

K>1

, to bounds in which the right-hand members grow much slower than linearly with

N
+
1

N+1

and with

n
+
1

n+1

, respectively. In this paper it is shown that such a sharpening is impossible. The following result is proved: for each

ϵ
>
0

\epsilon >0

, there are fixed values

C
>
0
,
K
>
1

C>0, K>1

and a sequence of

(
N
+
1
)
×
(
N
+
1
)

(N+1)\times (N+1)

matrices

A
N

A_N

, satisfying the resolvent condition, such that
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="double-vertical-bar left-parenthesis upper A Subscript upper N Baseline right-parenthesis Superscript n Baseline double-vertical-bar greater-than-or-equal-to upper C left-parenthesis upper N plus 1 right-parenthesis Superscript 1 minus epsilon">

‖
(

A
N

)
n

‖
≥
C
(
N
+
1

)

1
−
ϵ

\|(A_N)^n\|\ge C(N+ 1)^{1-\epsilon }

=
C
(
n
+
1

)

1
−
ϵ

=C(n+1)^{1-\epsilon }

for

N
=
n
=
1
,
2
,
3
,
…

N=n=1,2,3,\ldots

. The result proved in this paper is also relevant to matrices

A
A

whose

ϵ
\epsilon

-pseudospectra lie at a distance not exceeding

K
ϵ

K\epsilon

from the unit disk for all

ϵ
>
0

\epsilon >0

.
Improvements to the general number field sieve for discrete logarithms in prime fields. A comparison with the gaussian integer method
Authors: Joux Antoine , Lercier Reynald
Published: February 2003

In this paper, we describe many improvements to the number field sieve. Our main contribution consists of a new way to compute individual logarithms with the number field sieve without solving a very large linear system for each logarithm. We show that, with these improvements, the number field sieve outperforms the gaussian integer method in the hundred digit range. We also illustrate our results by successfully computing discrete logarithms with GNFS in a large prime field.
On the Assessment of Through-Wall Circumferential Cracks in Steam Generator Tubes With Tube Supports
Authors: Wang Xin , Reinhardt Wolf
Published: February 2003

The assessment of steam generator tubes with defects is of great importance for the life extension of steam generators. Circumferential through-wall cracks are the most severe of all tube circumferential defects, and usually require plugging of the affected tubes. The assessment of the tubes with through-wall circumferential cracks or cracks projected to become through-wall can be conducted using the failure assessment diagram (FAD) approach. This approach requires the calculation of the stress intensity factor and the limit load. The available stress intensity factor and limit load solutions for cracked tubes do not include the constraining effect of the tube supports. In the present paper, it is shown that this can be overly conservative. Solutions for stress intensity factors and limit loads are presented for tubes with circumferential through-wall cracks including the effect from the tube support plates. Different values of support spacing are considered. Based on these solutions, the assessment of a typical steam generator tube is demonstrated.
BEM Solution With Minimal Energy Technique for the Geometrical Inverse Heat Conduction Problem in a Doubly Connected Domain
Authors: Choi Chang-Yong , Jo Jong Chull
Published: February 2003

This article addresses the use of boundary element method in conjunction with minimal energy technique for solving a geometrical inverse heat conduction problem. The problem considered in this study is to estimate the unknown inner boundary position in an irregular-shaped hollow body of which the inner boundary surface is subjected to a specified temperature condition. For solving the problem, first boundary element equations are converted into the quadratic programming problem by minimizing the energy functional with a constraint, next a hypothetical inner boundary is defined such that the actual inner boundary is located interior of the hypothetical solution domain, then temperatures at hypothetical inner boundary are determined to meet the constraints of measurement error in inner surface temperatures, and finally boundary element analysis is performed for the position of an unknown boundary. Based on these main solution procedures, an effective detection algorithm is provided. In addition, the solution method is numerically tested to investigate the effects of measurement errors on the accuracy of estimation.
Parallel Numerical Prediction of Pulverized Coal Particle Flow in Bifurcator-Type Flow Splitters
Authors: Frank Th. , Schneider H. , Bernert K. , Pachler K.
Published: February 2003

This paper deals with the numerical simulation of two-phase flows based on the solution of the Navier-Stokes equations with a k−ε turbulence model for the gas phase and a particle tracking model of the disperse phase fulfilling the framework of the Eulerian-Lagrangian (PSI-cell) approach. The numerical procedures for the two phases are based on multigrid and domain decomposition methods applied to a block-structured grid. Due to the enormous numerical effort of such flow simulations the entire solving procedure has been parallelized for computers of MIMD architecture. The paper gives a short description of the applied and developed numerical methods. Furthermore the numerical simulation of a particle laden gas flow through a flow splitter from the area of power engineering is presented as an example for a real world application of the numerical approach.
Limit Load Bounds for the mα Multiplier
Authors: Reinhardt W. D. , Seshadri R.
Published: February 2003

Limit analysis is an important tool to assess the integrity of a structure. Successive elastic modulus adjustment, in particular, can simulate the plastic stress redistribution in a structure at the limit state (plastic collapse). Several limit load estimates have been developed based on the stress and strain distribution within a component. The bounding nature of these estimates is examined in this paper. Particular emphasis is given to the limit load estimate mα, which has been proposed to give improved limit load predictions from partly converged stress distributions in the structure. Bounds on the accuracy of these mα predictions are derived.
Experimental Investigation of Heat Exchanger Tubesheet Hole Enlargement
Authors: Shuaib A. N. , Merah N. , Khraisheh M. K. , Allam I. M. , Al-Anizi S. S.
Published: February 2003

An experimental study has been conducted to evaluate the effect of roller expansion of heat exchanger tubes in enlarged tubesheet holes on joint strength, tube wall reduction (i.e., thinning), and strain hardening of the tubes and surrounding tubesheet ligaments. Different levels of tube-to-tubesheet hole clearance, or overtolerance (OT), were investigated to simulate tubesheet in-service, and during-maintenance, hole enlargement process. The experimental results have shown that, in spite of increasing overtolerance level by up to seven times the maximum value allowed by the Tubular Exchanger Manufacturer Association (TEMA) standard, the average strength of the test joints has not declined below the strength of joints in the allowed TEMA OT range. Percent wall reduction (WR) of the expanded tube was found to increase linearly with increasing overtolerance value; although its maximum value remained well below the wall reduction limit for which a joint is rejected in industry. An observed increase in hardness of the expanded tube material is evidence of the high degree of strain hardening to which the expanded tubes are subjected compared with the surrounding ligaments. Pull-out forces, calculated using existing analytical methods, were found to compare well with the experimental results.
Development of triode-type carbon nanotube field-emitter arrays with suppression of diode emission by forming electroplated Ni wall structure
Authors: Jung J. E. , Choi J. H. , Park Y. J. , Lee H. W. , Jin Y. W. , Chung D. S. , Park S. H. , Jang J. E. , Hwang S. Y. , Ko T. Y. , Choi Y. S. , Cho S. H. , Lee C. G. , You J. H. , Lee N. S. , Yoo J. B. , Kim J. M.
Published: February 2003

Triode-type field-emitter arrays were developed by screen printing a photosensitive paste including single-walled carbon nanotubes. Ni wall structure (NWS) was electroplated to form a thick gate to suppress diode emission induced by strong electric strengths due to an anode potential and to focus electron beams to their destined color subpixels. It was observed in computer simulations, as well in experiments that the NWS with the optimum thickness was effective in reducing the diode emission and enhancing electron-beam focusing by modifying electrical potentials around the carbon nanotube emitters. Our fully sealed field-emission display panel using the field-emitter arrays with the NWS demonstrated full color moving images without serious diode emission and with satisfactory color separation.
Effect of annealing temperature on the electron emission characteristics of silicon tips coated with Ba0.67Sr0.33TiO3 thin film
Authors: Kang W. P. , Wisitsora-at A. , Davidson J. L. , Tan O. K. , Zhu W. G. , Li Q. , Xu J. F.
Published: February 2003

Electron emission from an array of silicon tips coated with Ba0.67Sr0.33TiO3 (BST) ferroelectric thin film was systematically investigated by varying the sol–gel BST annealing temperature from 650 to 800 °C. It was found that the turn-on electric field of BST-coated silicon tips tend to decrease as the BST annealing temperature increases, except for the 750 °C annealing temperature case that has a considerably lower turn-on field than that of 800 °C. Analysis of the emission data using Fowler–Nordheim plots suggested that a higher annealing temperature would result in lower effective work function. To better understand this effect, solid-state BST–silicon junction current–voltage measurements for different annealing temperatures were also studied. The analysis suggests that the conduction mechanism of BST–silicon junction conforms to a space-charge limited injection current model with shallow and deep traps. The higher BST annealing temperature, the shallower the trap was found to be and the quasi-Fermi level was nearer to the conduction band. It can be deduced that a higher annealing temperature results in higher activation of ionic conduction. This higher activation increases carrier concentration, raises the Fermi level toward the conduction band, thus reduces the effective work function, and thereby enhances field emission. In addition, it was found that the BST film annealed at 750 °C has relatively lower electron trap density than other cases. Lower electron trap density may be responsible for its relatively high emission efficiency.
Influence of the electronic structure on the field electron emission from carbon nanotubes
Authors: Filip V. , Nicolaescu D. , Tanemura M. , Okuyama F.
Published: February 2003

The classical statistical-tunneling approach for the electron field emission is applied for carbon nanotubes. Detailed computations for differential emission currents reveal very close peak shapes for the armchair and zigzag geometries, thus suggesting there is very little influence of the form of the electronic energy dispersion relations on the bulk field emission currents. For carbon nanotubes of practical width, an approximate semianalytical procedure is developed to compute the differential and total emission currents for virtually any type of dispersion relations. After validation for the armchair and zigzag geometries, this procedure may be further simplified into the frame of a fictitious confined two-dimensional free electron model. Some conclusions are drawn from the comparison of the computed field emission currents (through the simplified procedure) with present experimental data and a fully analytical expression for the total bulk field emission current is obtained for practical use.
Emission site control in carbon nanotube field emitters by focused ion and laser irradiation
Authors: Sawada A. , Iriguchi M. , Zhao W. J. , Ochiai C. , Takai M.
Published: February 2003

Multiwalled carbon nanotubes on aluminum or indium tin oxide layers were irradiated with gallium focused ion beams (FIBs) to induce defects and increase emission sites of carbon nanotubes (CNTs). A turn-on voltage was found to decrease from 460 to 220 V by ion irradiation at a dose of 1×1015/cm2, corresponding to turn-on fields from 3.7 to 1.8 V/μm. However, noticeable improvements in emission characteristics were not observed as a result of high-dose FIB irradiation at and above 1×1016/cm2. Because of the local temperature rise due to the intense FIB this irradiation resulted in melting of CNTs. The third harmonic of a neodymium-doped yttrium fluoride (Nd:YLF) laser light was irradiated over screen-printed CNT cathodes, which resulted in turn-on voltage decreasing from 400 to 320 V, corresponding to turn-on fields from 3.2 to 2.6 V/μm, with increased emissions by a factor of 6.
Emission characteristics of NbC/Nb field emitter array cathodes
Authors: Mackie W. A. , Southall L. A. , Xie Tianbao , Cabe G. L. , McClelland P. H.
Published: February 2003

We report fabrication and emission testing of NbC/Nb field emitter array cathodes. Previous work found carbide materials resistant to sputtering, to poor vacuum conditions, and to environments with oxygen ambient. In this work, emitters were deposited in arrays nominally having 0.5-μm-diam gate apertures using a lift-off layer and common techniques. Electron beam heated PVD was used throughout with deposition rates of 0.2–0.3 nm/s. Vacuum conditions during deposition were crucial to avoid inclusion of excessive amounts of oxygen. Micrographs of emitter cross sections allowed analysis of system variables, deposition rate, substrate temperature, and lift-off layer thickness. Typical deposition techniques used 300 nm of niobium followed immediately by 250 nm of NbC giving a tip cone of NbC on a truncated base cone of Nb. Emission testing confirmed the benefit of using carbide material where lower turn-on voltages and increased emission stability were realized over emitters made solely from refractory metals. Currents of 50 μA per single emitter tip were obtained while operating in 10−7 Torr ambient pressure. Emitter operation in limited partial pressures of oxygen did not degrade emission while improvements were noted in current stability while operating in limited pressures of hydrogen.
Effects of the interface and surface nanostructures on field emission of amorphous diamond film
Authors: Chen Jian , Xu N. S. , Deng S. Z. , She J. C. , Chen Jun
Published: February 2003

Details are given of a systematic experimental study into the effect of interface structure on the field emission properties of nanostructures using amorphous diamond (a-D) films. The field electron emission experiments indicates a better field emission characteristic after predepositing a metal (Al or Ti) interlayer. The effect of chemical etching of silicon substrate on the field emission of a-D film/silicon has been studied systematically. In addition, surface features of the film considered to be responsible for low field emission are discovered. Based on this latter finding, a new mechanism named field-induced transform step enhanced emission mechanism, which is responsible for electron emission from a-D film, is presented.
Degradation behavior of low-voltage cathodoluminescence of a ZnS:Ag,CI phosphor screen under a panel sealing environment
Authors: Park Z. M. , Jeon D. Y. , Jin Y. W. , Cha S. N. , Kim J. M.
Published: February 2003

We investigated the degradation characteristics of a low-voltage cathodoluminescence (CL) of ZnS:Ag,CI phosphor screen under the environment of the panel sealing process. Auger electron spectroscopy and CL measurements showed that compositional changes occurred in the surface layer of the phosphor screen. The oxide layer formed during the panel sealing process influenced the initial drop in CL intensity of the phosphor screen and the carbon adsorption under electron bombardment. We used x-ray photoelectron spectroscopy and plasmon energy loss to investigate the changes of carbon bonding in the surface layer of the phosphor screen. During prolonged electron bombardment, the CL of the phosphor screen decayed due to the accumulation of carbon. The longer the electron bombardment time, the more graphitic the surface became.
Silicon metal–oxide–semiconductor field effect transistor/field emission array fabricated using chemical mechanical polishing
Authors: Hong Ching-yin , Akinwande Akintunde I.
Published: February 2003

An integrated lightly doped drain-metal–oxide–semiconductor field effect transistor (LD-MOSFET) is used to control the electron supply of a silicon field emission array (FEA), resulting in low voltage switching and stabilization of emission current. The LD-MOSFET-driven field emission array was fabricated using isotropic and anisotropic etching of silicon, oxidation sharpening, chemical vapor deposition, and chemical mechanical polishing. Current–voltage characterization of the LD-MOSFET-driven FEA demonstrated modulation of electron emission by the MOSFET gate voltage and the reduction of current fluctuation.
Preparation and characterization of ZnGa2O4 phosphor synthesized with an optimized combustion process
Authors: Kim Jin Young , Kang Jong Hyuk , Lee Dong Chin , Jeon Duk Young
Published: February 2003

A ceramic synthesis technique, combustion synthesis, is explored to produce blue-emitting ZnGa2O4 phosphors. This technique involves the reaction of metal nitrates with a glycine as an organic fuel. In this article, the effects of processing parameters such as the ratio of glycine to ZnGa2O4 and the heat treatment are reported. The variation of the ratio of glycine to ZnGa2O4 introduces the compositional change in the as-synthesized ZnGa2O4, which in turn seriously influences the luminescence properties. Furthermore, the subsequent heat treatment of the as-synthesized one increases the intensity of the luminescence just after the combustion reaction. In particular, the samples heat treated at above 1200 °C show a strong blue-emission peak at 445 nm, which is attributed to the single phase and well-crystallized ZnGa2O4 oxides in the spinel structure.
Growth and evaluation of nanostructured carbon films for triode field emitter application
Authors: Park Kyung Ho , Han Hyung Jun , Choi Seungho , Lee Kyung Moon , Lee Soonil , Koh Ken Ha
Published: February 2003

To identify the deposition conditions that can minimize the nanotube density in the nanostructured carbon films without compromising the emission properties, we carried out a systematic investigation of the effect of deposition conditions on the emission properties and the structure of the nanostructured carbon films. Catalyst-layer thickness, methane concentration, deposition time, deposition pressure, and substrate temperature were the main deposition parameters we investigated. Within the parameter range for nanoparticle-dominant growth, substrate temperature and deposition time were the two factors that had the largest effect on the variation of the turn-on field. However, catalyst-layer thickness and methane concentration turned out to be the factors allowing the minimization of nanotube density with rather small concomitant variations of the turn-on field. A 50 h test showed that the emission stability of a nanoparticle film was better than that of a multiwall nanotube film with comparable emission characteristics. The feasibility of triode fabrication was verified by the successful deposition of a nanoparticle-film cathode of about 8 μm diameter using the conventional photolithography process.
Ultraviolet-Raman studies of SrTiO3 ultrathin films on Si
Authors: Hilt Tisinger L. , Liu R. , Kulik J. , Zhang X. , Ramdani J. , Demkov A. A.
Published: February 2003

Stoichiometric and nonstoichiometric SrTiO3 (STO) films less than 50 nm were grown by molecular beam epitaxy on Si substrates for characterization with UV-Raman spectroscopy. All the films grown have first order phonon Raman scattering as the crystal symmetry has been altered due to threading dislocations and local vicinal strain at defect sites. Strong phonon scattering and hardening of the phonon modes is seen in Ti-rich films while Sr-rich films have a decrease in the phonon scattering intensity when compared with stoichiometric thin films. Excess Ti leads to a high density of planar boundaries and different chemical phases lowering the overall crystal symmetry of STO. The Sr-rich sample compensates for excess Sr by forming SrO Ruddlesden–Popper layers in the perovskite structure.
Electromagnetic characterization of nanoimprint mold inspection
Authors: Deng Yunfei , Neureuther Andrew R.
Published: February 2003

The electromagnetic effects of opaque mold materials in exposure, and complementary mask inspection in the innovative nanoimprint technique of White and Wood are explored through simulation. For a wavelength of 365 nm and 40 nm features in an opaque layer with 10% transmission, an extinction coefficient of more than 3 is important for a high transmission in the open features and a refractive index larger than 2 is also useful. For complementary mask inspection the leakage is largest for the polarization perpendicular to the edge and depends on edge length. The leakage is not a strong function of misalignment and rises less than linearly with the separation between the facing surfaces of the two masks. Defects one-third of a feature size are one-twentieth of a wavelength in size, and with filtering of the radiated spectrum can contribute up to 10% of the signal associated with leakage from a complete feature.
Stripping of photoresist using a remote thermal Ar/O2 and Ar/N2/O2 plasma
Authors: Brussaard G. J. H. , Letourneur K. G. Y. , Schaepkens M. , van de Sanden M. C. M. , Schram D. C.
Published: February 2003

Photoresist is etched using a remote thermal (cascaded arc) plasma in Ar/O2 and Ar/O2N2 mixtures. Very high etch rates, up to 200 nm/s, are achieved at low substrate temperatures (350 K) and low electron and ion temperatures (<0.5 eV). The addition of small amounts of nitrogen (3%) leads to an increase in etch rate. The etch rate in Ar/O2/N2 also increases with time during the etching process. The details of the plasma and surface chemistries are not yet well understood.
Simultaneous surface topography and spin-injection probability
Authors: Bullock D. W. , LaBella V. P. , Ding Z. , Thibado P. M.
Published: February 2003

A spin-polarized electron current is injected into a p-type GaAs(110) surface at 100 K using a polycrystalline ferromagnetic Ni scanning tunneling microscope tip. The injected electrons recombine to the valence band and emit circularly polarized light, and the degree of the light polarization is related to the degree of the electron polarization at the instant of recombination. Details of how to simultaneously measure the surface topography and obtain a pixel-by-pixel map of the spin-injection probability are discussed. The degree of light polarization is found to change when the electrons are injected into a clean, flat terrace versus over a step. However, the terrace-to-step polarization differences are systematically reduced as the energy of the electron is reduced.
Large-area patterning of ∼50  nm structures on flexible substrates using near-field 193 nm radiation
Authors: Kunz R. R. , Rothschild M. , Yeung M. S.
Published: February 2003

Near-field contact exposures through a chromeless phase-shifting mask at 193 nm are used to create arbitrarily shaped structures as small as 45 nm on thin (∼10–15 μm) sheets of polyimide. The thin sheets make smooth, stable laminates on carrier wafers through van der Waals interactions for processing like normal silicon wafers and can be removed to enable conformal mask contact during exposure. Further, the thin substrates are flexible enough to allow for curved and/or shaped photonic surfaces. When a silicon-containing bilayer resist is used, high aspect ratio (>4:1) structures 50–80 nm in width are obtained following oxygen-plasma pattern transfer. Optical simulations using the finite-difference time-domain model are used to predict the near-field intensity distribution, and its results are compared to the experiments. This model indicates that with unpolarized light and a contact gap ⩽25 nm, exposure latitudes in excess of 15% are possible for printing isolated, arbitrarily shaped features 50–60 nm wide over areas limited in size only by the mask dimensions (>10 cm square).
Microstructural study of Pt contact on p-type GaN
Authors: Kim Jong Kyu , Jang Ho Won , Kim Chong Cook , Je Jung Ho , Rickert Kimberly A. , Kuech Thomas F. , Lee Jong-Lam
Published: February 2003

Using synchrotron x-ray scattering the evolution of the biaxial strain at the interface of the Pt layer (100 Å) with p-type GaN was investigated as a function of annealing temperature. Furthermore, the effects of the biaxial strain on the change of ohmic contact resistivity were interpreted. The Pt layer grew epitaxially on GaN with the relationships of Pt [111]//GaN [0001] and Pt [11̄0] //GaN [112̄0]. Due to a lattice mismatch between Pt and GaN, a biaxial tensile strain (+0.9%) to the Pt layer and a compressive strain (−0.9%) to the GaN substrate were introduced in the as-deposited state. After annealing at 450 °C, the strains were fully relaxed and the position of the surface Fermi level moved 0.21 eV toward the valence band maximum. Furthermore, the contact resistivity decreased by 1 order of magnitude. The results provide evidence that the change of the interfacial strain causes the movement of the surface Fermi level position in the band gap of GaN, leading to a change in the magnitude of contact resistivity.
Influence of pattern density in nanoimprint lithography
Authors: Gourgon C. , Perret C. , Micouin G. , Lazzarino F. , Tortai J. H. , Joubert O. , Grolier J.-P. E.
Published: February 2003

Polymer selection and critical dimension control across the wafer are key parameters for the nanoimprint lithography technique. This nanotechnology requires polymers having a low glass transition temperature Tg combined with a good etch resistance. In this work, three different polymers have been evaluated. The influence of the temperature and pressing time is analyzed to clarify the correlation between polymer behavior and printing uniformity as a function of the pattern density. Measurements of the polymer residual thickness show that the printing uniformity is strongly correlated with the thermal properties of the polymer.
Line edge roughness and photoresist percolation development model
Authors: Ma Yuansheng , Shin J. , Cerrina Franco
Published: February 2003

In this article we present a three-dimensional dissolution percolation model based on the percolation concept and on the propagation of a front over a regular lattice of cells. The model describes the development process of the chemically amplified resists like UV-6. It is shown that, starting from this model, normalized resist thickness and dissolution rate can be characterized, line/space pattern may be generated, then line edge roughness and developing surface roughness can be analyzed and predicted in a statistical sense. There is a good agreement in the trends between our simulation results and experimental data.
Fabrication of subwavelength-size aperture for a near-field optical probe using various microfabrication procedures
Authors: Choi S. S. , Jung M. Y. , Kim D. W. , Kim J. W. , Boo J. H.
Published: February 2003

We successfully fabricated subwavelength-size silicon oxide apertures on a cantilever array as a near-field optical probe. Various semiconductor processes were utilized for subwavelength-size aperture fabrication. The anisotropic etching of the Si substrate by alkaline solutions followed by anisotropic crystal orientation dependent oxidation, anisotropic plasma etching, and isotropic oxide etching was carried out. 2, 3, and 4 μm size dot arrays were initially photolithographically patterned on a Si(100) wafer. After fabrication of a V-groove shape by anisotropic etching, oxide growth at 1000 °C was performed to have an oxide etch mask. The oxide layer on the Si(111) plane has been utilized as an etch mask for plasma dry etching and water-diluted HF wet etching for subwavelength-size aperture fabrication. A Au thin layer was deposited on the fabricated oxide aperture on the cantilever array. After this procedure, the initial opening, 300 nm of the oxide aperture was reduced down to ∼95 nm.
Improved thermal stability of Ni silicide on Si (100) through reactive deposition of Ni
Authors: Kim Gi Bum , Yoo Do-Joon , Baik Hong Koo , Myoung Jae-Min , Lee Sung Man , Oh Sang Ho , Park Chan Gyung
Published: February 2003

The effect of reactive deposition of Ni on the thermal stability of Ni silicide has been investigated in this study. In the case of room-temperature-deposited Ni, the agglomeration of Ni silicide, which induced the thermal instability during subsequent annealing, started to appear at 600 °C and the sheet resistance was increased abruptly after high-temperature anneals. However, when the Ni was deposited on the heated Si substrate (reactive deposition of Ni), the sheet resistance of Ni silicide film exhibited a constant value of about 7.91 Ω/□ at the whole reaction temperature, especially at 900 °C.
Atomic force microscopy of nickel dot arrays with tuning fork and nanotube probe
Authors: Rozhok S. , Jung S. , Chandrasekhar V. , Lin Xiwei , Dravid Vinayak P.
Published: February 2003

The advantages of tuning fork scanning force microscopy are combined with the unique properties of carbon nanotubes to improve the spatial resolution of atomic force microscopy (AFM) images of nickel dot arrays. These arrays have high relief features that prevent the resolution of the actual dot size and shape with a regular cantilever tip. The modification of two key parts of a commercial AFM, the force sensor, and the probe allowed the acquisition of true data on feature size and shape. AFM images of Ni dot arrays were taken using conventional optical detection of a commercial cantilever, tuning fork with attached commercial cantilever tip, and tuning fork with attached multiwalled carbon nanotube. The resolutions of the AFM images were compared, and it was shown that probing with a carbon nanotube provided a 30% improvement of lateral resolution compared to a conventional AFM tip.
Adaptive run-to-run control and monitoring for a rapid thermal processor
Authors: Qin S. Joe , Scheid Glen W. , Riley Terrence J.
Published: February 2003

Process reproducibility is a challenging problem in semiconductor manufacturing as the component size shrinks and the manufacturing complexity increases. This article proposes a new adaptive run-to-run controller for intermittent batch operations and applies it to a rapid thermal annealing (RTA) process at Advanced Micro Devices. The adaptive controller has a self-monitoring component and requires little process knowledge to set up. The success of the controller is demonstrated on an AST SHS 2800 RTA system. Improvement was made to reduce the first wafer effects and lot-to-lot variability due to disturbances.
Fabrication of high resolution x-ray masks using diamond membrane for second generation x-ray lithography
Authors: Marumoto Kenji , Yabe Hideki , Aya Sunao , Kise Koji , Ami Shigeto , Sasaki Kei , Watanabe Hiroshi , Itoga Kenji , Sumitani Hiroaki
Published: February 2003

Second generation x-ray lithography (PXL-II) has been proposed to extend proximity x-ray lithography to the 50 nm generation and beyond while keeping a high throughput. Diamond membrane, which enables high power and shorter x-ray irradiation, is a key material for PXL-II. In this article, we describe the fabrication of ultrafine patterns of W–Ti absorber on thinned diamond membranes. By optimization of the etching conditions, about 30 nm W–Ti patterns with aspect ratios of about 10 were successfully fabricated. The dependence of pattern edge roughness of the absorber on the surface roughness of the diamond has also been investigated, and it has been shown that 3 nm rms roughness was enough to obtain the pattern quality equivalent to that on a SiC membrane. For narrower gap exposure with x-ray masks with thick diamond membrane in PXL-II, the flatness of the mask top surface has been studied, and we developed x-ray masks with a flatness of less than 1 μm by modifying the support ring geometry.
The 4He Trimer: Structure and Energetics of a Very Unusual Molecule
Authors: Di Paola Cono , Gianturco Franco A. , Delgado-Barrio Gerardo , Miret-Artés Salvador , Villarreal Pablo
Published: February 2003

The 4He3 weakly interacting system is analysed by constructing the full interaction as a sum of two-body (2B) potentials chosen among the most recent proposals from the literature. The spatial density distributions of the three bound atoms are obtained using a diffusion Monte Carlo (DMC) algorithm and a stochastic analysis under specific geometric constraints is carried out with the resulting densities in order to recover a more conventional structural picture for such floppy system. The total binding energies were obtained with the chosen potentials analysed in the present work, using the DMC algorithm, and are compared with previous published results. The ensuing spatial distributions are analysed in some detail to select the dominant structures from a conventional triangular description of this very floppy molecule.
Ab initio Study of the Li-CO van der Waals Complex
Authors: Lukeš Vladimír , Laurinc Viliam , Ilčin Michal , Biskupič Stanislav
Published: February 2003

The adiabatic potential energy surface (PES) of the Li-CO complex in the van der Waals region, described by Jacobi coordinates (r = 1.15 Å, R, Θ), was investigated using the supermolecular coupled-clusters CCSD(T) method. Our calculations indicate minima for bent arrangements. The first minimum was found on the carbon side of CO molecule at R = 5.27 Å (Θ = 50.7°) with a well depth of De = -167.2 μEh. The second minimum is indicated at R = 5.35 Å (Θ = 148.7°) with a well depth of De = -121.9 μEh. The saddle point is localised at θ = 111.5° and R = 5.35 Å. The physical origin of the weak interaction studied was analysed by the intermolecular perturbation theory based on the single determinant UHF wave function. The separation of the interaction energies shows that the locations of the predicted stable bent structures are primarily determined by the anisotropy of the repulsive Heitler-London exchange penetration and attractive dispersion and induction energy components.
Some Approximate Atomic and Molecular Energy Formulas
Authors: Politzer Peter , Jalbout Abraham F. , Jin Ping
Published: February 2003

We have tested several approximate formulas that relate atomic and molecular energies to the electrostatic potentials at the nuclei, V0 and V0,A, respectively. They are based upon the assumption that the chemical potentials can be neglected relative to V0 and V0,A. Exact, Hartree-Fock and density-functional values were used for the latter. The results are overall encouraging; the errors in the energies generally decrease markedly as the nuclear charges Z increase and the assumptions become more valid. Improvement is needed, however, in fitting the V0 and V0,A to Z.
The Character of Low-Lying Excited States of Mixed-Ligand Metal Carbonyls. TD-DFT and CASSCF/CASPT2 Study of [W(CO)4L] (L = ethylenediamine, N,N'-dialkyl-1,4-diazabutadiene) and [W(CO)5L] (L = pyridine, 4-cyanopyridine)
Authors: Záliš Stanislav , Vlček Antonín , Daniel Chantal
Published: February 2003

This contribution presents the results of the TD-DFT and CASSCF/CASPT2 calculations on [W(CO)4(MeDAB)] (MeDAB = N,N'-dimethyl-1,4-diazabutadiene), [W(CO)4(en)] (en = ethylenediamine), [W(CO)5(py)] (py = pyridine) and [W(CO)5(CNpy)] (CNpy = 4-cyanopyridine) complexes. Contrary to the textbook interpretation, calculations on the model complex [W(CO)4(MeDAB)] and [W(CO)5(CNpy)] show that the lowest W→MeDAB and W→CNpy MLCT excited states are immediately followed in energy by several W→CO MLCT states, instead of ligand-field (LF) states. The lowest-lying excited states of [W(CO)4(en)] system were characterized as W(COeq)2→COax CT excitations, which involve a remarkable electron density redistribution between axial and equatorial CO ligands. [W(CO)5(py)] possesses closely-lying W→CO and W→py MLCT excited states. The calculated energies of these states are sensitive to the computational methodology used and can be easily influenced by a substitution effect. The calculated shifts of [W(CO)4(en)] stretching CO frequencies due to excitation are in agreement with picosecond time-resolved infrared spectroscopy experiments and confirm the occurrence of low-lying M→CO MLCT transitions. No LF electronic transitions were found for either of the complexes studied in the region up to 4 eV.
Effective Hamiltonian and Intermediate Hamiltonian Formulations of the Fock-Space Coupled-Cluster Method
Authors: Meissner Leszek , Gryniaków JarosłaW
Published: February 2003

Various aspects of the effective Hamiltonian and intermediate Hamiltonian formulations are discussed in the context of the Fock-space coupled-cluster method. Problems that occur when single-reference methods of solving the Schrödinger equation need to be generalized to the multireference (MR) cases are pointed out. These problems make the generalization nontrivial, especially in the case of the most powerful coupled-cluster (CC) method. It is shown how some specific features of one of the basic MR-CC schemes, the Fock-space CC method, can be used to obtain a simple, yet very effective version of the method. This requires, however, switching from the effective Hamiltonian to the intermediate Hamiltonian formulation. The intermediate Hamiltonian version of the Fock-space CC method is discussed in detail and all its advantages over the standard one are emphasized.