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1.
P. N. Vinod 《Journal of Materials Science: Materials in Electronics》2011,22(9):1248-1257
The specific contact resistance of the screen-printed Ag contacts in the silicon solar cells has been investigated by applying
two independent test methodologies such as three-point probe (TPP) and well-known transfer length model (TLM) test structure
respectively. This paper presents some comparative results obtained with these two measurement techniques for the screen-printed
Ag contacts formed on the porous silicon antireflection coating (ARC) in the crystalline silicon solar cells. The contact
structure consists of thick-film Ag metal contacts patterned on the top of the etched porous silicon surface. Five different
contact formation temperatures ranging from 725 to 825 °C for few minutes in air ambient followed by a short time annealing
step at about 450 °C in nitrogen ambient was applied to the test samples in order to study the specific contact resistance
of the screen-printed Ag metal contact structure. The specific contact resistance of the Ag metal contacts extracted based
on the TPP as well as TLM test methodologies has been compared and verified. It shows that the extraction procedure based
on the TPP method results in specific contact resistance, ρ
c
= 2.15 × 10−6 Ω-cm2 indicating that screen-printed Ag contacts has excellent ohmic properties whereas in the case of TLM method, the best value
of the specific contact resistance was found to be about ρ
c
= 8.34 × 10−5 Ω-cm2. These results indicate that the ρ
c
value extracted for the screen-printed Ag contacts by TPP method is one order of magnitude lower than that of the corresponding
value of the ρ
c
extracted by TLM method. The advantages and limitations of each of these techniques for quantitatively evaluating the specific
contact resistance of the screen-printed Ag contacts are also discussed. 相似文献
2.
P. N. Vinod 《Journal of Materials Science: Materials in Electronics》2009,20(10):1026-1032
The SEM and specific contact resistance measurements of the Ag metal contact formed by applying a fire-through process on
the shallow emitter region of the silicon solar cell have been investigated. The metal contact consists of screen-printed
Ag paste patterned on the silicon nitride (Si3N4) deposited over the n+-Si emitter region of the solar cell. The sintering step consists of a rapid firing step at 800 °C or above in air ambient.
This is followed by an annealing step at 450 °C in nitrogen ambient. It enables to drive the Ag metal paste onto the Si3N4 layer and facilitates the formation of an Ag metal/p-Si contact structure. It serves as the top metallization for the screen-printed
silicon solar cell. The SEM measurement shows that sintering of the Ag metal paste at 800 °C or above causes the Ag metal
to firmly coalesce with the underlying n+-Si surface. A thin layer of conductive glassy layer is also presents at the interface of the Ag metal and n+-Si surface. The electrical quality of the contact structure was characterized by measuring the specific contact resistance,
ρ
c
(in Ω-cm2) using the iteration technique based on the power loss calculation for the solar cell. It shows that best value of ρ
c
= 2.53 × 10−5 Ω-cm2 is estimated for the Ag metal contact sintered at temperature above 800 °C. This value of ρ
c
is two orders of magnitude lower than the typical value of ρ
c
= 3 × 10−3 Ω-cm2 reported previously for the Ag contacts of the solar cell. Such low value of ρ
c
for the Ag metal contacts indicates that fire-through process results in excellent ohmic properties. The plot of the ρ
c
versus impurity doping level (N
s
) shows that measured value of the ρ
c
follows a linear relationship with the N
s
as predicted by the theory for the heavily doped semiconductor surface. Hence, carrier injection across the Schottky barrier
height is quite appropriate to explain the observed ohmic properties of the Ag metal contacts on the n+-Si surface of the silicon solar cell.
相似文献
P. N. VinodEmail: |
3.
P. N. Vinod 《Journal of Materials Science: Materials in Electronics》2007,18(8):805-810
The establishment of a suitable contact formation methodology is a critical part of the technological development of any metal-to-semiconductor
contact structure. Many test structures and methodologies have been proposed to estimate the specific contact resistance (ρc) of the planar ohmic contacts formed on the heavily doped semiconductor surface. These test structures are usually processed
on the same wafer to monitor a particular process. In this study, new experimental procedure has been evolved to assess the
value of ρc of the screen-printed front silver (Ag) thick-film metal contact to the silicon surface. The essential feature of this methodology
is that it is an iteration technique based on the calculation of power loss associated with various resistive components of
the solar cell normalized to the unit cell area. Therefore, this method avoids the complexity of making the design of any
lay out of a standard contact resistance test structure like transmission line model (TLM) or Kelvin resistor, etc. It was
shown that value of specific contact resistance of the order of 1.0 × 10−5 Ω−cm
2 is measured for the Ag metal contacts formed on the n+ silicon surface. This value is much lower than the ρc data previously reported for the screen-printed Ag contacts. The sintering process of the front metal contact structure at
different furnace setting is carried out to understand the possible wet interaction and metal contact formation as a function
of the firing. Therefore, the study is further extended to study the peak firing temperature dependence of the ρc of screen-printed Ag metal contacts. It will help to assess the specific contact resistance of the ohmic contacts as a function
of firing temperature of sintering process.
相似文献
P. N. VinodEmail: |
4.
P. Narayanan Vinod 《Journal of Materials Science: Materials in Electronics》2008,19(7):594-601
The front grid contact is particularly important and requires a low contact resistance which represents the resistance associated
with the barrier at the interface of the metal and semiconductor contact structure. Often applied metal contacts are fired
at a higher temperature (typically above 700 °C) in air ambient, which produces ohmic contact on both surface of the photovoltaic
device. The specific contact resistance is one of the important device parameter on studying the interfacial properties of
the metalization system. Therefore, a reliable methodology to assess the ohmic losses of the applied metal contact structure
is required. It shows that it is rather simple and reliable to assess the electrical quality of the applied metal contacts
by quantifying the total ohmic losses of the solar cell associated with the various resistive components of the solar cell
normalized to unit cell area. It has been recently demonstrated that with a new experimental procedure, namely iteration method
based on the calculation of power loss (ICPL) associated with the contact resistance of the front Ag thick-film metal contacts,
a much reliable value of the specific contact resistance of the order of ≅10−5 Ω cm2 can be extracted for the planar ohmic contacts. In this work, the specific contact resistance of the planar ohmic contacts
formed on the heavily doped n+ region of the solar cells were studied on large number of finished cells by two independent methods: (i) standard three-point
probe (TPP) and (ii) iteration technique based on the calculation of the power loss (ICPL) associated with the contact resistance
of the front Ag contacts of the solar cell normalized to unit cell area. It shows that the value of specific contact resistance
measured by both methods are desirably much lower than the expected value of 10−3 Ω cm2 for the screen-printed Ag metal contacts of the photovoltaic cells used for the A.M. 1.5 applications. Using the iteration,
each resistive components of the solar cell normalized to unit cell area were directly evaluated. It is shown that by combining
the measurements of specific contact resistance of the planar ohmic contacts and ohmic losses of the cell, it gives a direct
and non-destructive diagnostic tool to qualitatively check the electrical quality of the applied Ag metal contacts.
相似文献
P. Narayanan VinodEmail: |
5.
Alexander Klushin Alexander Golubov Werner Prusseit Hermann Kohlstedt 《Journal of Low Temperature Physics》1997,106(3-4):265-269
In order to optimize the series array performance of Y Ba2Cu3O7−x (YBCO) grain boundary shunted junctions, a method to determine and control the junction resistance Rs and Au/YBCO contact resistivity ρ
c
has been developed. 200 nm thick c-oriented YBCO films were grown by intermittent thermal coevaporation on bicrystal yttria-stabilized
zirconia substrates. A gold contact overlayer of thickness dn was deposited in situ. Normal junction resistances have been measured as a function of dn and shunt width w. It was shown that, in accordance with theoretical estimates, the junction shunt resistance is essentially
controlled by the c-axis Au/YBCO interface specific resistance and scales as
. The product ρ
c
ρ
n
≃ 3.10−14 Ω2
cm
3 was estimated from the experimental data, leading to ρ
c
≈ 10−8 Ωcm
2 for typical values of ρ
n
for gold thin films. 相似文献
6.
A. Andreone F. Fontana M. Iavarone M. Salluzzo R. Vaglio 《Journal of Low Temperature Physics》1997,107(5-6):527-532
High quality c-axis oriented films of the intriguing intermetallic superconducting compound YNi2B2C have been obtained “in situ” by magnetron sputtering on MgO substrates held at about 800°C. The films showed maximum Tc=15.3 K, †Tc≈0.1 K, room temperature resistivity ρ≈50μΩ·cm, critical current Jc≈105 A/cm2 and Bc2≈6 T. Superconducting films were also obtained on Al2O3 and LaAlO3 single-crystal substrates. From the ρ(T) dependence a value of the Debye temperature Θ
D
=330±20 K can be deduced. At low temperatures the resistivity follows a quadratic power law possibly indicative of a high
value of the electron-phonon interaction parameter λ. In order to clarify the role of λ in these compounds, point contact
spectroscopy measurements have been performed on YNi2B2C and HoNi2B2C bulk samples prepared by inductive melting using a Low Temperature Scanning Tunneling Microscope (LTSTM). In the point contact
regime clear evidence of a superconducting gap have been found in both compounds, corresponding to a moderate strong coupling
behaviour (2†/KTc≈3.8). 相似文献
7.
Yongping Pu Haidong Wu Jifeng Wei Bo Wang 《Journal of Materials Science: Materials in Electronics》2011,22(9):1479-1482
As a positive temperature coefficient of resistivity (PTCR) material, Ba0.92Ca0.05(Bi0.5Na0.5)0.03TiO3 ceramics with donor doping of Nb5+ and acceptor doping of Mn2+ were prepared by a conventional mixed oxide method. The influence of contents of Nb5+ and Mn2+ on the microstructure and PTCR characteristics of Ba0.92Ca0.05(Bi0.5Na0.5)0.03TiO3 ceramics sintered at 1,360°C for 2 h was investigated. The result showed that the Curie temperature (T
c) was shifted to a lower temperature with increasing of the content of Nb5+ and the resistance jump (ρmax/ρmin) was enhanced with doping of Mn2+. The grain size of ceramic sample decreased with increasing of contents of donor Nb5+ and acceptor Mn2+. The Ba0.92Ca0.05(Bi0.5Na0.5)0.03TiO3 ceramic with 0.4 mol%Nb5+ and 0.04 mol%Mn2+ exhibited a low ρRT of 5.0 × 102 Ω cm, a typical PTCR effect of ρmax/ρmin > 103, and a T
c of 158°C. 相似文献
8.
Features of the contact melting in thin-film structures comprising an aluminum layer with a thickness of h
1 = 5 μm and a metal (Ti, Ni, Mo) or semiconductor (Si, Ge) sublayer (h
2 = 0.1 μm) on a single crystal silicon plate (h
3 = 500 μm) have been studied. The contact melting was caused by single rectangular electric pulses with a current density
of j < 9 × 1010 A/m2 and a duration of τ = 100–1000 μs passing through the Al layer. The duration and rate of melting in the samples were determined
using voltage waveforms measured by an oscillograph. A method has been developed based on an analysis of the mechanisms of
contact interaction in the Al film—sublayer system (with allowance for experimental data on the time of sublayer dissolution
in the Al film) for estimating the coefficients of mutiphase diffusion of the system components during the passage of a current
pulse. 相似文献
9.
S T Lakshmikumar 《Bulletin of Materials Science》1995,18(3):223-228
Contact resistance measurements of chromium contacts deposited by partially ionized beam deposition on transparent conducting
indium tin oxide (ITO) were performed. These provide a direct experimental evidence of the influence of interfacial chemical
interaction on the contact resistance. The interfacial reactivity is controlled by modifying the energy and flux of ionized
chromium atoms deposited on ITO employing a specially designed partially ionized deposition system with very high ionization
efficiency. The true contact resistivityρ
c is obtained by iteratively correcting the experimentally measured values for the finite sheet resistance of the ITO layer.ρ
c decreases linearly with the energy of the ionized chromium. Auger sputter profiling shows no structural modifications at
the interface due to a change in the energy of the chromium atoms, confirming that the observed change in the contact resistivity
is directly related to interfacial chemical bonding of the atoms with the oxygen atoms in the ITO leading to a local increase
of carrier concentration and lower interfacial resistance. 相似文献
10.
J KANUNGO L SELEGÅRD C VAHLBERG K UVDAL H SAHA S BASU 《Bulletin of Materials Science》2010,33(6):647-651
Nano porous silicon (PS) was formed on p-type monocrystalline silicon of 2–5 Ω cm resistivity and (100) orientation by electrochemical anodization method using HF
and ethanol as the electrolytes. High density of surface states, arising due to its nano structure, is responsible for the
uncontrolled oxidation in air and for the deterioration of the PS surface with time. To stabilize the material PS surface
was modified by a simple and low cost chemical method using PdCl2 solution at room temperature. X-ray photoelectron spectroscopy (XPS) was performed to reveal the chemical composition and
the relative concentration of palladium on the nanoporous silicon thin films. An increase of SiO2 formation was observed after PdCl2 treatment and presence of palladium was also detected on the modified surface. I–V characteristics of Al/PS junction were studied using two lateral Al contacts and a linear relationship was obtained for Pd
modified PS surface. Stability of the contact was studied for a time period of around 30 days and no significant ageing effect
could be observed. 相似文献
11.
A Rohatgi P Doshi A Ebong S Narasimha T Krygowski J Moschner 《Bulletin of Materials Science》1999,22(3):383-390
Rapid and potentially low-cost processing techniques are analyzed and applied toward the fabrication of high-efficiency Si
solar cells. (i) A technology that can simultaneously form the phosphorus emitter, boron BSF, andin situ oxide in a single high-temperature furnace step or: simultaneously diffused, textured, and AR coated process (STAR) is presented.
(ii) A high quality screen-printed (SP) contact methodology is developed that results in fill factors of 0·785–0·790 on monocrystalline
Si. (iii) Aluminum back surface field (Al-BSF) formation is studied in detail to establish the process conditions that result
in optimal BSF action. (iv) Screen-printing of Al conductor paste and rapid thermal processing (RTP) are integrated into the
BSF procedure, and effective recombination velocities (S
eff) as low as 200 cm/s are demonstrated on 2·3 Ω-cm Si with this rapid thermal processing of screen-printed contacts, Al alloyed
BSF processes. (v) A novel passivation scheme consisting of a dielectric stack (plasma silicon nitride on top of a rapid thermal
oxide) is developed to reduce the surface recombination velocity (S) to ≈ 10 cm/s at the 1·3 Ω-cm Si surface. The important feature of this stack passivation scheme is its ability to withstand
a high-temperature anneal (700–850°C) without degradation in surface recombination velocity. This feature is critical for
most current commercial processes that utilize SP contact firing. (vi) Finally, the individual processes are integrated to
form high-efficiency, manufacturable devices. Solar cell efficiencies of 17% and >19% are achieved on FZ Si with SP and evaporated
(photolithography) contacts, respectively. 相似文献
12.
Measurements were made of the transition resistivities of an aluminum-porous silicon contact and the resistivity of the surface
region of the porous material after short-term annealing in an inert medium at temperatures between 300 and 550 °C. It was
shown that the parameters of the contacts are determined by the pore morphology, the annealing temperature, and the plasma-chemical
etching process. For porous silicon formed on p-Si, annealing reduces the transition resistivities by several orders of magnitude. In this case, the resistivity of the surface
region of porous silicon decreases sharply. The results are analyzed from the point of view of the passivating effect of hydrogen
in the porous silicon.
Pis’ma Zh. Tekh. Fiz. 24, 45–51 (March 26, 1998) 相似文献
13.
P. A. Shcheglov S. A. Men’shikh L. F. Rybakova Yu. Ya. Tomashpol’skii 《Inorganic Materials》2000,36(4):380-384
A modified method for preparing barium and lead titanate films is suggested, which combines precipitation from solution and
elements of sol-gel processing. The ∼1-μm-thick BaTiO3/Pt and PbTiO3/Pt films deposited on Pt foil are transparent, show good adhesion, and have the 1 : 1 : 3 stoichiometry. The films are finegrained,
with a mean grain size of 0.1–0.2 μm. The barium titanate films are characterized byt
C = 110-125°C, ε20 = 167-500, tanδ20 = 0.015-0.06, εmax = 1050,P
s= 3.2 μC/cm2,E
c = 14 kV/cm, ρ = (5-7) × 109 Ω cm, andV
br = 80-150 kV/cm. The lead titanate films are characterized byc/a = 1.056, ε20 = 105-110, tanδ20 = 0.11-0.16,P
s = 4.1 μC/cm2,E
c = 34 kV/cm, ρ = (0.8-3.0) × 109 Ω cm, andV
br = 50-100 kV/cm. 相似文献
14.
R Viswanathan S N Yedave S T Bendre S M Kanetkar S M Chaudhari S B Ogale 《Bulletin of Materials Science》1991,14(2):435-441
Ion beam and thermally-induced interface reactions between highT
c superconducting thin film of Y1Ba2Cu3O7−x
and metal overlayer of Ag are studied with a view to control the interfacial property of contact resistance. The interface
reaction is induced by 100 keV Ar+ ion beam with different ion dose values ranging from 5 × 1013 to 3×1014 ions/cm2. The YBaCuO film-metal interface is characterized by using the small angle XRD to study the structural properties of the
interfacial phases. The electrical property of the interface, specifically contact resistance, has been investigated for different
dose values and thermal treatments. Three-probe vs four-probe configuration has been adopted to measure the contact resistance. 相似文献
15.
Mesoporous silicon granules with high surface area were synthesized directly from pure silica sodalite single crystals, with
the starting shape retained. The sodalite single crystals were reduced by a magnesiothermal process in vacuum at 630 °C. The
X-ray diffraction patterns indicate the presence of crystal silicon. Transmission electron microscopy studies reveal that
the obtained silicon granules are composed of a monocrystalline surface with an island-like mesoporous internal structure.
The results of N2 adsorption and desorption analysis indicate that the surface area is around 308 m2 g−1 and the single point pore volume is 0.37 cm3 g−1. The photoluminescence emission centered at 2.7 eV may be due to both an oxidized surface and quantum confinement effects.
These results reveal that the silicon granules possess a different microstructure from those of etched silicon films. The
present synthetic design correlates the microporous zeolite and mesoporous silicon together and gives a new way for enlarging
the structural diversity of porous silicon crystal. 相似文献
16.
B. I. Belevtsev Yu. F. Komnik V. I. Odnokozov A. V. Fomin 《Journal of Low Temperature Physics》1984,54(5-6):587-605
Electrical and superconducting properties of indium films condensed in a H2 atmosphere (pressurep
H
2=6×10−6 to 1.4×10−4 Torr) onto a substrate cooled with liquid helium are investigated. As hydrogen content is increased, a continuous increase
in residual resistivity ρ* is observed, permitting systematic study of the resistance vs. temperature dependenceR(T) and the superconducting transition temperatureT
c on approaching the metal-insulator transition (MIT). With regard to ρ*, four regimes of conductivity can be observed: (1)
conductivity with a positive temperature resistance coefficient (TRC), (2) conductivity with a small, constant, negative TRC,
(3) conductivity under weak localization with ΔR (T) ∼ln T or
type corrections, (4) hopping conductivity.T
c rises continuously with ρ* and reaches its peak (∼5.2K) in the second regime. A further increase of ρ* leads to a decrease
ofT
c and complete suppression of superconductivity. The experimental dependenceR(T) is compared with theory. TheT
c variation on approaching the MIT and the relation between Mooij's rule and the superconducting properties are discussed. 相似文献
17.
The crystal structure, oxidation resistance, and magnetic properties of SmCo7−x
Si
x
(x=0, 0.4, 0.6, and 0.9) permanent magnetic alloys were investigated systematically. It is found that the addition of silicon
in the as-cast SmCo7 ingot plays an important role in stabilizing TbCu7 phase and improving inherent oxidation resistance. For the bulk nanocrystalline SmCo7−x
Si
x
magnets, the oxidation resistance remarkably enhances but the corresponding Curie temperature T
c
and maximum energy product (BH)max exhibit a decreasing trend with the increase in Si content x. For the typical SmCo6.4Si0.6 nanocrystalline magnet, its final mass gain was about 1.71 mg/cm2 after oxidation at 500 °C for 100 h, indicating the enhanced inherent oxidation resistance. Its T
c
and (BH)max were about 708 °C and 35.4 kJ/m3, respectively. 相似文献
18.
The structure of polyethyleneterephthalate bristles drawn about five times in the amorphous state and subsequently crystallized
at temperatures between 100 and 260‡ C has been studied by means of small-angle X-ray scattering. In addition density, heat
of fusion and wide-angle scattering behaviour were measured. For comparison, similar experiments were carried out with undrawn
samples. The results showed that the degree of crystallinity of PET cannot be calculated from density data on the basis of
a simple two-phase model, since the effective densitiesρ
c
*
andρ
a
*
of the crystalline and amorphous regions depend strongly on crystallization and drawing conditions. With rising crystallization
temperature the size of the mosaic blocks building up the crystalline layers and their longitudinal mutual order increase
whereas the volume fraction of the crystalline region is only rather slightly effected by the annealing temperature. The difference
between the effective densityρ
c
*
and the “X-ray density”ρ
c of the crystalline layers is supposed to be caused by lattice vacancies in the boundaries of the mosaic blocks. 相似文献
19.
I. M. Abdulagatov N. G. Polikhronidi A. Abdurashidova S. B. Kiselev J. F. Ely 《International Journal of Thermophysics》2005,26(5):1327-1368
The isochoric heat capacity of pure methanol in the temperature range from 482 to 533 K, at near-critical densities between
274.87 and 331.59 kg· m−3, has been measured by using a high-temperature and high-pressure nearly constant volume adiabatic calorimeter. The measurements
were performed in the single- and two-phase regions including along the coexistence curve. Uncertainties of the isochoric
heat capacity measurements are estimated to be within 2%. The single- and two-phase isochoric heat capacities, temperatures,
and densities at saturation were extracted from experimental data for each measured isochore. The critical temperature (Tc = 512.78±0.02K) and the critical density (ρc = 277.49±2 kg · m−3) for pure methanol were derived from the isochoric heat-capacity measurements by using the well-established method of quasi-static
thermograms. The results of the CVVT measurements together with recent new experimental PVT data for pure methanol were used to develop a thermodynamically self-consistent Helmholtz free-energy parametric crossover
model, CREOS97-04. The accuracy of the crossover model was confirmed by a comprehensive comparison with available experimental
data for pure methanol and values calculated with various multiparameter equations of state and correlations. In the critical
and supercritical regions at 0.98Tc≤ T ≤ 1.5Tc and in the density range 0.35ρc ≤ ρ leq 1.65 ρc, CREOS97-04 represents all available experimental thermodynamic data for pure methanol to within their experimental uncertainties. 相似文献
20.
Akbar Ali Abdul Majid M. Nawaz Saleh 《Journal of Materials Science: Materials in Electronics》2008,19(3):267-269
Deep level transient spectroscopy has been used to study thermally activated defects in silicon. It has been observed that
different annealing temperatures activate different defects in silicon, which were lying on inactive sites before annealing.
Two deep mid-gap levels at energy positions E
c −0.48 eV and E
c −0.55 eV were found to be introduced by different heat treatments. It is also noted that heat treatment at 1,250 °C suppresses
the concentration of deep level at E
c −0.23 eV and enhances the concentration of deep level at E
c −0.25 eV, while heat treatment at 950 °C has an opposite effect. Annealing response of the level at E
c −0.48 eV is found different to the annealing response of the level at E
c −0.55 eV which suggests them two different levels. 相似文献