共查询到20条相似文献,搜索用时 31 毫秒
1.
A specially designed experiment is performed for investigating gate-induced
drain leakage (GIDL) current in 90nm CMOS technology using lightly-doped
drain (LDD) NMOSFET. This paper shows that the drain bias $V_{\rm D}$ has a
strong effect on GIDL current as compared with the gate bias $V_{\rm G}$ at the
same drain--gate voltage $V_{\rm DG}$. It is found that the difference between
$I_{\rm D}$ in the off-state $I_{\rm D}-V_{\rm G}$ characteristics and the
corresponding one in the off-state $I_{\rm D}-V_{\rm D}$ characteristics, which is
defined as $I_{\rm DIFF}$, versus $V_{\rm DG}$ shows a peak. The difference between
the influences of $V_{\rm D}$ and $V_{\rm G}$ on GIDL current is shown
quantitatively by $I_{\rm DIFF}$, especially in 90nm scale. The difference is
due to different hole tunnellings. Furthermore, the maximum $I_{\rm DIFF
}$($I_{\rm DIFF,MAX})$ varies linearly with $V_{\rm DG}$ in logarithmic coordinates
and also $V_{\rm DG}$ at $I_{\rm DIFF,MAX}$ with $V_{\rm F}$ which is the characteristic
voltage of $I_{\rm DIFF}$. The relations are studied and some related
expressions are given. 相似文献
2.
Effect of F doping on capacitance-voltage characteristics of SiCOH low-k films metal-insulator-semiconductor structure 下载免费PDF全文
This paper investigates the capacitance--voltage
($C$--$V$) characteristics of F doping SiCOH low dielectric constant
films metal--insulator--semiconductor structure. The F doping SiCOH
films are deposited by decamethylcyclopentasiloxane (DMCPS) and
trifluromethane (CHF7755, 6855 http://cpb.iphy.ac.cn/CN/10.1088/1674-1056/19/5/057701 https://cpb.iphy.ac.cn/CN/article/downloadArticleFile.do?attachType=PDF&id=111779 F-SiCOH, low-k dielectrics, capacitance--voltage
characteristic Project supported by the National
Natural Science Foundation of China (Grant No.~10575074). 2/4/2009 12:00:00 AM This paper investigates the capacitance--voltage
($C$--$V$) characteristics of F doping SiCOH low dielectric constant
films metal--insulator--semiconductor structure. The F doping SiCOH
films are deposited by decamethylcyclopentasiloxane (DMCPS) and
trifluromethane (CHF$_{3})$ electron cyclotron resonance plasmas.
With the CHF$_{3}$/DMCPS flow rate ratio from 0 to 0.52, the
positive excursion of $C$--$V$ curves and the increase of flat-band
voltage $V_{\rm FB}$ from $-6.1$~V to 32.2~V are obtained. The
excursion of $C$--$V$ curves and the shift of $V_{\rm FB}$ are
related to the change of defects density and type at the Si/SiCOH
interface due to the decrease of Si and O concentrations, and the
increase of F concentration. At the CHF$_{3}$/DMCPS flow rate ratio
is 0.12, the compensation of F-bonding dangling bond to Si dangling
bond leads to a small $V_{\rm FB}$ of 2.0~V. 半导体结构;电压特性;电容电压;绝缘体;薄膜;金属;电子回旋共振等离子体;兴奋剂 This paper investigates the capacitance-voltage (C-V) characteristics of F doping SiCOH low dielectric constant films metal-insulator-semiconductor structure. The F doping SiCOH films are deposited by decamethylcyclopentasilox-ane [DMCPS) and trifluromethane (CHF3) electron cyclotron resonance plasmas. With the CHF3/DMCPS flow rate ratio from 0 to 0.52, the positive excursion of C-V curves and the increase of fiat-band voltage VFB from -6.1 V to 32.2V are obtained. The excursion of C-V curves and the shift of VFB are related to the change of defects density and type at the Si/SiCOH interface due to the decrease of Si and O concentrations, and the increase of F concentration. At the CHF3/DMCPS flow rate ratio is 0.12, the compensation of F-bonding dangling bond to Si dangling bond leads to a small VFB of 2.0V. 相似文献
3.
This paper reports that a novel type of suspended ZnO nanowire field-effect
transistors (FETs) were successfully fabricated using a
photolithography process, and their electrical properties were
characterized by I--V measurements. Single-crystalline ZnO
nanowires were synthesized by a hydrothermal method, they were used
as a suspended ZnO nanowire channel of back-gate field-effect
transistors (FET). The fabricated suspended nanowire FETs showed a
p-channel depletion mode, exhibited high on--off current ratio of
~105. When VDS=2.5 V, the peak transconductances
of the suspended FETs were 0.396 μS, the oxide capacitance was
found to be 1.547 fF, the pinch-off voltage VTH was about
0.6 V, the electron mobility was on average 50.17 cm2/Vs. The
resistivity of the ZnO nanowire channel was estimated to be
0.96× 102Ω cm at VGS = 0 V. These
characteristics revealed that the suspended nanowire FET fabricated
by the photolithography process had excellent performance. Better
contacts between the ZnO nanowire and metal electrodes could be
improved through annealing and metal deposition using a focused ion
beam. 相似文献
4.
A novel Si-rich SiN bilayer passivation with thin-barrier AlGaN/GaN HEMTs for high performance millimeter-wave applications 下载免费PDF全文
Zhihong Chen 《中国物理 B》2022,31(11):117105-117105
We demonstrate a novel Si-rich SiN bilayer passivation technology for AlGaN/GaN high electron mobility transistors (HEMTs) with thin-barrier to minimize surface leakage current to enhance the breakdown voltage. The bilayer SiN with 20-nm Si-rich SiN and 100-nm Si$_{3}$N$_{4}$ was deposited by plasma-enhanced chemical vapor deposition (PECVD) after removing 20-nm SiO$_{2}$ pre-deposition layer. Compared to traditional Si$_{3}$N$_{4}$ passivation for thin-barrier AlGaN/GaN HEMTs, Si-rich SiN bilayer passivation can suppress the current collapse ratio from 18.54% to 8.40%. However, Si-rich bilayer passivation leads to a severer surface leakage current, so that it has a low breakdown voltage. The 20-nm SiO$_{2}$ pre-deposition layer can protect the surface of HEMTs in fabrication process and decrease Ga-O bonds, resulting in a lower surface leakage current. In contrast to passivating Si-rich SiN directly, devices with the novel Si-rich SiN bilayer passivation increase the breakdown voltage from 29 V to 85 V. Radio frequency (RF) small-signal characteristics show that HEMTs with the novel bilayer SiN passivation leads to $f_{\rm T}/f_{\rm max}$ of 68 GHz/102 GHz. At 30 GHz and $V_{\rm DS} = 20$ V, devices achieve a maximum $P_{\rm out}$ of 5.2 W/mm and a peak power-added efficiency (PAE) of 42.2%. These results indicate that HEMTs with the novel bilayer SiN passivation can have potential applications in the millimeter-wave range. 相似文献
5.
A 4H-SiC trench MOSFET structure with wrap N-type pillar for low oxide field and enhanced switching performance 下载免费PDF全文
An optimized silicon carbide (SiC) trench metal-oxide-semiconductor field-effect transistor (MOSFET) structure with side-wall p-type pillar (p-pillar) and wrap n-type pillar (n-pillar) in the n-drain was investigated by utilizing Silvaco TCAD simulations. The optimized structure mainly includes a p$+$ buried region, a light n-type current spreading layer (CSL), a p-type pillar region, and a wrapping n-type pillar region at the right and bottom of the p-pillar. The improved structure is named as SNPPT-MOS. The side-wall p-pillar region could better relieve the high electric field around the p$+$ shielding region and the gate oxide in the off-state mode. The wrapping n-pillar region and CSL can also effectively reduce the specific on-resistance ($R_{\rm on,sp}$). As a result, the SNPPT-MOS structure exhibits that the figure of merit (FoM) related to the breakdown voltage ($V_{\rm BR}$) and $R_{\rm on,sp}$ ($V_{\rm BR}^{2}R_{\rm on,sp}$) of the SNPPT-MOS is improved by 44.5%, in comparison to that of the conventional trench gate SJ MOSFET (full-SJ-MOS). In addition, the SNPPT-MOS structure achieves a much faster-witching speed than the full-SJ-MOS, and the result indicates an appreciable reduction in the switching energy loss. 相似文献
6.
This article investigates an improved 4H-SiC trench gate metal-oxide-semiconductor field-effect transistor (MOSFET) (UMOSFET) fitted with a super-junction (SJ) shielded region. The modified structure is composed of two n-type conductive pillars, three p-type conductive pillars, an oxide trench under the gate, and a light n-type current spreading layer (NCSL) under the p-body. The n-type conductive pillars and the light n-type current spreading layer provide two paths to and promote the diffusion of a transverse current in the epitaxial layer, thus improving the specific on-resistance ($R_{\rm on,sp}$). There are three p-type pillars in the modified structure, with the p-type pillars on both sides playing the same role. The p-type conductive pillars relieve the electric field ($E$-field) in the corner of the trench bottom. Two-dimensional simulation (silvaco TCAD) indicates that $R_{\rm on,sp }$ of the modified structure, and breakdown voltage ($V_{\rm BR}$) are improved by 22.2% and 21.1% respectively, while the maximum figure of merit (${\rm FOM}=V^{2}_{\rm BR}/R_{\rm on,sp}$) is improved by 79.0%. Furthermore, the improved structure achieves a light smaller low gate-to-drain charge ($Q_{\rm gd}$) and when compared with the conventional UMOSFET (conventional-UMOS), it displays great advantages for reducing the switching energy loss. These advantages are due to the fact that the p-type conductive pillars and n-type conductive pillars configured under the gate provide a substantial charge balance, which also enables the charge carriers to be extracted quickly. In the end, under the condition of the same total charge quantity, the simulation comparison of gate charge and OFF-state characteristics between Gauss-doped structure and uniform-doped structure shows that Gauss-doped structure increases the $V_{\rm BR}$ of the device without degradation of dynamic performance. 相似文献
7.
This paper calculates the transition wavelengths and probabilities
of the two-electron and one-photon (TEOP) transition from the
$(3{\rm s}^{-1}_{1/2}4{\rm d}_{j})_{J=1,2}$ to $(3{\rm
p}^{-1}_{3/2}4{\rm s}_{1/2})_{J=1}$ and the $(3{\rm
p}^{-1}_{1/2}4{\rm s}_{1/2})_{J=1}$ to $(3{\rm d}^{-1}_{j}4{\rm
d}_{j'})_{J=1,2}$ for highly charged Ni-like ions with atomic number
$Z$ in the range $47\leq Z\leq92$. In the calculations, the
multi-configuration Dirac--Fock method and corresponding program
packages GRASP92 and REOS99 were used, and the relativistic effects,
correlation effects and relaxation effects were considered
systematically. It is found that the TEOP transitions are very
sensitive to the correlation of electrons, and the probabilities
will be enhanced sharply in some special $Z$ regions along the
isoelectronic sequence. The present TEOP transition wavelengths are
compared with the available data from some previous publications,
good agreement is obtained. 相似文献
8.
Density functional theory (DFT) (B3P86) of Gaussian 03 has been used to optimize the structure of the Cr2 molecule, a transition metal element molecule. The result shows that the ground state for the Cr2 molecule is a 13- multiple state, indicating that there exists a spin polarization effect in the Cr2 molecule. Meanwhile, we have not found any spin pollution because the wave function of the ground state does not mingle with wave functions of higher-energy states. So the ground state for Cr2 molecule being a 13-multiple state is indicative of spin polarization effect of the Cr2 molecule among transition metal elements, that is, there are 12 parallel spin electrons in the Cr2 molecule. The number of non-conjugated electrons is greatest. These electrons occupy different spatial orbitals so that the energy of the Cr2 molecule is minimized. It can be concluded that the effect of parallel spin in the Cr2 molecule is larger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell Sorbie potential functions with the parameters for the ground state and other states of the Cr2 molecule are derived. The dissociation energy De for the ground state of the Cr2 molecule is 0.1034eV, equilibrium bond length Re is 0.3396 nm, and vibration frequency we is 73.81cm^-1. Its force constants f2, f3 and f4 are 0.0835, -0.2831 and 0.3535 aJ. nm^-4 respectively. The other spectroscopic data for the ground state of the Cr2 molecule ωeχe, Be and αe are 1.2105, 0.0562 and 7.2938 x 10^-4cm^-1 respectively. 相似文献
9.
Magnetic susceptibility, specific heat, and neutron powder diffraction measurements have been performed on polycrystalline Li$_{2}$Co(WO$_{4}$)$_{2}$ samples. Under zero magnetic field, two successive magnetic transitions at $T_{\rm N1}\sim 9.4$ K and $T_{\rm N2}\sim 7.4$ K are observed. The magnetic ordering temperatures gradually decrease as the magnetic field increases. Neutron diffraction reveals that Li$_{2}$Co(WO$_{4}$)$_{2}$ enters an incommensurate magnetic state with a temperature dependent $\bm k$ between $T_{\rm N1}$ and $T_{\rm N2}$. The magnetic propagation vector locks-in to a commensurate value $\bm k = (1/2, 1/4, 1/4)$ below $T_{\rm N2}$. The antiferromagnetic structure is refined at 1.7 K with Co$^{2+}$ magnetic moment 2.8(1) $\mu_{\rm B}$, consistent with our first-principles calculations. 相似文献
10.
Rong Zhang 《中国物理 B》2022,31(6):63402-063402
The effect of collision energy on the magnetically tuned $^{6}$Li-$^{6}$Li Feshbach resonance (FR) is investigated theoretically by using the coupled-channel (CC) method for the collision energy ranging from 1 μ$ {\rm K} \cdot {k}_{\rm B}$ to 100 μ$ {\rm K} \cdot {k}_{\rm B}$. At the collision energy of 1 μ$ {\rm K} \cdot {k}_{\rm B}$, the resonance positions calculated are 543.152 Gs (s wave, the unit $1 {\rm Gs}=10^{-4} {\rm T}$), 185.109 Gs (p wave $|m_{l}| = 0$), and 185.113 Gs (p wave $|m_{l}| = 1$), respectively. The p-wave FR near 185 Gs exibits a doublet structure of 4 mGs, associated with dipole-dipole interaction. With the increase of the collision energy, it is found that the splitting width remains the same (4 mGs), and that the resonance positions of s and p waves are shifted to higher magnetic fields with the increase of collision energy. The variations of the other quantities including the resonance width and the amplitude of the total scattering section are also discussed in detail. The thermally averaged elastic rate coefficients at $T=10$, 15, 20, 25 K are calculated and compared. 相似文献
11.
Novel material for nonvolatile ovonic unified memory (OUM)-Ag11In12Te26Sb51 phase change semiconductor 下载免费PDF全文
In this paper, Ag_{11}In_{12}Te_{26}Sb_{51} phase change semiconductor films have been prepared by dc sputtering. The crystallization behaviour of amorphous Ag_{11}In_{12}Te_{26}Sb_{51} thin films was investigated by using differential scanning calorimetry and x-ray diffraction. It was found that the crystallization temperature is about 483K and the melting temperature is 754.8K and the activation energy for crystallization, E_a, is 2.07eV. The crystalline Ag_{11}In_{12}Te_{26}Sb_{51} films were obtained using initializer. The initialization conditions have a great effect on the sheet resistance of Ag_{11}In_{12}Te_{26}Sb_{51} films. We found that the effect of the initialization condition on the sheet resistance can be ascribed to the crystallinity of Ag_{11}In_{12}Te_{26}Sb_{51} films. The sheet resistance of the amorphous (R_{amo}) film is found to be larger than 1×10^6Ω and that of the crystalline (R_{cry}) film lies in the range from about 10^3 to 10^4Ω. So we have the ratio R_{amo}/R_{cry}=10^2~10^3, which is sufficiently large for application in memory devices. 相似文献
12.
The Ni/4H-SiC Schottky barrier diodes (SBDs) and transfer length
method (TLM) test patterns of Ni/4H-SiC Ohmic contacts were
fabricated, and irradiated with 1~MeV electrons up to a dose of
3.43× 1014~e/cm-2. After radiation, the forward
currents of the SBDs at 2~V decreased by about 50%, and the
reverse currents at -200~V increased by less than 30%. Schottky
barrier height (φ B ) of the Ni/4H-SiC SBD increased
from 1.20~eV to 1.21~eV under 0~V irradiation bias, and decreased
from 1.25~eV to 1.19~eV under -30~V irradiation bias. The
degradation of φ B could be explained by the variation
of interface states of Schottky contacts. The on-state resistance
(Rs) and the reverse current increased with the dose, which
can be ascribed to the radiation defects in bulk material. The
specific contact resistance (\rhoc) of the Ni/SiC Ohmic
contact increased from 5.11× 105~Ωega.cm2 to 2.97× 10-4~Ωega.cm2. 相似文献
13.
Investigations on spectroscopic parameters, vibrational levels, classical turning points and inertial rotation and centrifugal distortion constants for the X1∑+g state of sodium dimer 下载免费PDF全文
The density functional theory (B3LYP, B3P86) and the quadratic
configuration-interaction method including single and double
substitutions (QCISD(T), QCISD) presented in Gaussian03 program
package are employed to calculate the equilibrium internuclear
distance $R_{\rm e}$, the dissociation energy $D_{\rm e }$ and the
harmonic frequency $\omega _{\rm e}$ for the $X{}^{1}\Sigma^{ +
}_{\rm g}$ state of sodium dimer in a number of basis sets. The
conclusion is gained that the best $R_{\rm e}$, $D_{\rm e}$ and
$\omega _{\rm e}$ results can be attained at the
QCISD/6-311G(3df,3pd) level of theory. The potential energy curve at
this level of theory for this state is obtained over a wide
internuclear separation range from 0.16 to 2.0~nm and is fitted to
the analytic Murrell--Sorbie function. The spectroscopic parameters
$D_{\rm e}$, $D_{0}$, $R_{\rm e}$, $\omega _{\rm e}$,
$\omega _{\rm e}\chi _{\rm e}$,
$\alpha _{\rm e}$
and $B_{\rm e}$ are calculated to be 0.7219~eV,
0.7135~eV, 0.31813~nm, 151.63~cm$^{ - 1}$, 0.7288~cm$^{ - 1}$,
0.000729~cm$^{ - 1}$ and 0.1449~cm$^{ - 1}$, respectively, which are in good
agreement with the measurements. With the potential obtained at the
QCISD/6-311G(3df,3pd) level of theory, a total of 63 vibrational
states is found when $J=0$ by solving the radial Schr\"{o}dinger equation
of nuclear motion. The vibrational level, corresponding classical turning
point and inertial rotation constant are computed for each vibrational
state. The centrifugal distortion constants
($D_{\upsilon }\, H_{\upsilon }$,
$L_{\upsilon }$, $M_{\upsilon }$, $N_{\upsilon }$ and $O_{\upsilon })$ are
reported for the first time for the first 31 vibrational states when $J=0$. 相似文献
14.
The analytical transfer matrix method (ATMM) is applied to
calculating the critical radius $r_{\rm c}$ and the dipole
polarizability $\alpha_{\rm d}$ in two confined systems: the hydrogen
atom and the Hulth\'{e}n potential. We find that there exists a
linear relation between $r_{\rm c}^{1/2}$ and the quantum number $n_{r}$
for a fixed angular quantum number $l$, moreover, the three bounds
of $\alpha_{\rm d}$ ($\alpha_{\rm d}^{K}$, $\alpha_{\rm d}^{B}$,
$\alpha_{\rm d}^{U}$) satisfy an inequality:
$\alpha_{\rm d}^{K}\leq\alpha_{\rm d}^{B}\leq\alpha_{\rm d}^{U}$. A comparison
between the ATMM, the exact numerical analysis, and the variational
wavefunctions shows that our method works very well in the systems. 相似文献
15.
Hot carriers injection (HCI) tests for ultra-short channel n-MOSFET
devices were studied. The experimental data of short channel devices
(75--90\,nm), which does not fit formal degradation power law well,
will bring severe error in lifetime prediction. This phenomenon
usually happens under high drain voltage ($V_{\rm d}$) stress
condition. A new model was presented to fit the degradation curve
better. It was observed that the peak of the substrate current under
low drain voltage stress cannot be found in ultra-short channel
device. Devices with different channel lengths were studied under
different $V_{\rm d}$ stresses in order to understand the relations
between peak of substrate current ($I_{\rm sub}$) and channel
length/stress voltage. 相似文献
16.
本文考虑带有黑洞视界和宇宙视界的Kiselev时空.研究以黑洞视界和宇宙视界为边界的系统的热力学性质.统一地给出了两个系统的热力学第一定律;在黑洞视界半径远小于宇宙视界半径的情况下,近似地计算了通过宇宙视界和黑洞视界的热能.然后,探讨Kiselev时空的物质吸积特性.在吸积能量密度正比于背景能量密度的条件下给出黑洞的吸积率,讨论了黑洞吸积率与暗能量态方程参数的关系. 相似文献
17.
In the framework of density functional theory, using the plane-wave
pseudopotential method, the nitrogen vacancy ($V_{\rm N})$ in both
wurtzite and zinc-blende AlN is studied by the supercell approach.
The atom configuration, density of states, and formation energies of
various charge states are calculated. Two defect states are
introduced by the defect, which are a doubly occupied single state
above the valance band maximum (VBM) and a singly occupied triple
state below the conduction band minimum (CBM) for wurtzite AlN and
above the CBM for zinc-blende AlN. So $V_{\rm N}$ acts as a deep
donor in wurtzite AlN and a shallow donor in zinc-blende AlN. A
thermodynamic transition level $E({3 + } \mathord{\left/ {\vphantom
{{3 + } + }} \right. \kern-\nulldelimiterspace} + )$ with very low
formation energy appears at 0.7 and 0.6eV above the VBM in wurtzite
and zinc-blende structure respectively, which may have a wide shift
to the low energy side if atoms surrounding the defect are not fully
relaxed. Several other transition levels appear in the upper part of
the bandgap. The number of these levels decreases with the structure
relaxation. However, these levels are unimportant to AlN properties
because of their high formation energy. 相似文献
18.
The dependences of soft magnetic properties and microstructures of the
sputtered FeCo (=FeFeCo薄膜 溅射条件 软磁性 高饱和磁化强度 FeCo film, sputtering conditions, high saturation magnetization,
soft magnetic properties 2005-10-26 3/7/2006 12:00:00 AM The dependences of soft magnetic properties and microstructures of the sputtered FeCo (=Fe65Co35) films on Co underlayer thickness tCo, FeCo thickness tFeCo, substrate temperature Ts and taxget-substrate spacing dT-s are studied. FeCo single layer generally shows a high coercivity with no obvious magnetic anisotropy. Excellent soft magnetic properties with saturation magnetization μ0Ms of 2.35 T and hard axis coercivity Hch of 0.25 kA/m in FeCo films can be achieved by introducing a Co underlayer. It is shown that sandwiching a Co underlayer causes a change in orientation and reduction in grain size from 70 nm to about 10 nm in the FeCo layer. The magnetic softness can be explained by the Hoffmann's ripple theory due to the effect of grain size. The magnetic anisotropy can be controlled by changing dT-S, and a maximum of 14.3 kA/m for anisotropic field Hk is obtained with dT-S=18.0 cm. 相似文献
19.
Electron tunnelling phase time and dwell time through an associated delta potential barrier 下载免费PDF全文
The electron tunnelling phase time τP and dwell time τD through an associated delta potential barrier U(x) = ξδ(x) are calculated and both are in the order of 10^-17~10^-16s. The results show that the dependence of the phase time on the delta barrier parameter ξ can be described by the characteristic length lc = h^2/meξ and the characteristic energy Ec=meξ^2/h^2 of the delta barrier, where me is the electron mass, lc and Ec are assumed to be the effective width and height of the delta barrier with lcEc=ξ, respectively. It is found that TD reaches its maximum and τD = τp as the energy of the tunnelling electron is equal to Ec/2, i.e. as lc =λDB, λDB is de Broglie wave length of the electron. 相似文献
20.
Guiding of 150 keV O6+ ions through nanocapillaries in an uncoated Al2O3 membrane: special time dependence of the transmission profile width 下载免费PDF全文
<正>This paper reports that the transmission of O6+ ions with energy of 150keV through capillaries in an uncoated Al2O3 membrane was measured,and agreements with previously reported results in general angular distribution of the transmitted ions and the transmission fractions as a function of the tilt angle well fitted to Gaussian-like functions were observed.Due to using an uncoated capillary membrane,ourψc is larger than that using a gold-coated one with a smaller value of(?),which suggests a larger equilibrium charge Q∞in our experiment.The observed special width variation with time and a larger width than that using a smaller(?) were qualitatively explained by using mean-field classical transport theory based on a classical-trajectory Monte Carlo simulation. 相似文献