Platinum Metals in Ohmic Contacts to 111-V Semiconductors by D

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Platinum Metals in Ohmic Contacts to 111-V Semiconductors By D. G. Ivey Depart inent of Chemical and Materials Engineering, Lliiiver\it> of A41berta.Caiiada

Plulinum metals, particularly plutinum und pulladium, are used extensicel! in laic; resistance, relaticely stuble and laterally uniform ohmic contacts mude io semiconductor devires formed from Group III und 1'elements. Pulludium is primarily utilised as one component of u multilayer metullisuiion sirurture, improving utlhesion to the semiconductor, while platinum is commonly used us a diJjCrisionbarrier to minimise interdqfusion between metal und semiconductor componcwts. This paper describes the roles of platinum arid yaUudiuni in ohmic contacts, giues examples of their typical uiilisation and outlines the design considerations ussociared with the formation of reliable ohmic contucts.

Compound semiconductors formed from These devices are operated at high current elements in Groups I11 and V (111-V) of the densities and, as technology develops, are con- Periodic Table, such as GaAs and InP and related tinually undergoing a reduction in size. In order ternaries and quaternaries, have become impor- to link the active regions of the semiconductor tant materials for a number of microelectronic devices to the external circuit, contacts with low and optoelectronic applications. These include electrical resistance (ohmic contacts) are field effect transistors (FET), junction field effect required. The small dimensions of these devices transistors (JFET), high electron mobility tran- place severe processing constraints on the mate- sistors (HEMT) and heterojunction bipolar tran- rials used in the construction of these ohmic con- sistors (HBT), as well as photonic devices, such tacts. The main requirements of ohmic contacts as long-wavelength laser diodes, light-emitting are that they should have low contact resistance, diodes (LED) and photodetectors and solar cells. be thermally stable and have good adhesion and

I Selected Ohmic Contacts to 111-V Semiconductors Contact DopingDoping level, level, MinimumMinimum Annealing Refs. cm~3 contact temperature, resistance,resistance, rc, rc, OC C2 cm2

n-Type Pd-lnP 11 x x 1018 77x105 x 10-5 300300-350 - 350 1,21, 2 Pd/Ge/Au-lnP 11 x x loi7loi7 2.525x x 10 lo6 300300 - - 375 375 33 Pd/Ge-lnP 11 x x 10"10" 6x6x lob lob 400400 - - 450 450 33 PdlGe-GaAs 55 xx 1018 4x1074x107 400-415400-415 44

p-Type Pd/Pt/Au/Pd-lnGaP/GaAs 33 xx loi91018loi9 ii lofi 415-440415-440 55 Zn/Pd/Pt/Au-AIGa AdGa As 8.585x x lo-' 10' 440440 66 Ti/Pt/Au-InGaAs 55 xx 1018 6x10'6x10' 450450 7 7 Ti/Pt-InGaAs 55 xx 1018 4x10b4x10b 450450 88 Ti/Pt-InGaAs 1.515 x x 1018 3.434x x 10 10' 450450 99 Pd/Zn/Pd/Au-lnP 22 xx 1018 77X1O5 x 420420 - - 425 425 1010

Platinum Metals Rev., 1999, 43, (l), 2-12 2 lateral uniformity. These are all directly affected by the microstructure of the contact. Platinum metals are used extensively in ohmic contacts to 111-V semiconductors, as diffusion barriers or reactive components in multilayer metallisation schemes. Examples of typical contacts are given in the Table, together with their (b) minimum contact resistances. Highly doped

Formation of Ohmic Contacts Metal-semiconductor contacts can be divided 1 into two types, based on their current-voltage characteristics. Contacts which show rectifying Distance tmrn interface characteristics are called Schottky barriers or rectifying contacts, and contacts which have lin- Electron Energy ear current-voltage behaviour are referred to as (C) ohmic contacts. In practice, a contact is ohmic if the voltage drop across it is negligible com- Electron pared with the voltage drop across the device or specimen - the contact is thus not affecting the currendvoltage (IN) characteristics of the device. There are several methods for forming Metolliutim Semiconductor low resistance ohmic contacts, but manufacture of the most common commercial contacts always Fig. l(a) Schematic of an ohmic contact involves the formation of a very heavily doped structure to an n-type semiconductor; (b) Simplified plot of doping concentration of (> 5 x cm-’) thin layer of semiconductor 1Ol8 semiconductor in (a); ’ material on the semiconductor surface, imme- (c) Simplified energy band diagram of diately adjacent to the metal, see Figure 1. The metallisatiodsemiconductor interface region depletion region produced at the interface between the metal and the semiconductor is then so thin that field emission or tunneling of thin layered surfaces is by using an external charge carriers may take place, giving a contact dopant. The dopant, for example, zinc for with a very low resistance at zero bias. ptype and germanium for n-type semiconduc- Production of the highly doped surface can be tors, is deposited as a thin layer (of a few to tens achieved in two ways. One method involves of nanometres in thickness) on the semicon- growing a heavily doped epitaxial layer, for exam- ductor by electron beam evaporation and is usu- ple, by chemical vapour deposition (CVD) on ally driven into the semiconductor by solid state the semiconductor prior to metal deposition. diffusion, which requires heating the contact. The epitaxial layer is often a material with a These contacts are termed alloyed contacts and lower bandgap, such as In,,,Ga,,,As (E, = 0.75 the dopant metal is usually part of a multilayer ev) which is lattice matched to InP, or a graded metallisation scheme, the other possible metal In,Ga,.,As layer (graded to InAs at the surface) layers including adhesion layers, diffusion bar- (1 1).These contacts should not, at least in the- riers and capping layers to prevent oxidation ory, require subsequent annealing and are there- during annealing. fore referred to as non-alloyed contacts. In prac- In designing contacts to 111-V semiconductors tice, most of these contacts are still annealed to a number of factors have to be considered (1 2), attain optimum values of contact resistance. the most important probably being the contact The other method of producing the doped, resistance. Several other important factors have

Platinum Metals Rev., 1999, 43, (1) 3 to be taken into account, as contacts should conductor) and compound formation with both be stable over a wide temperature range, have the Group I11 and Group V elements (12). good lateral uniformity and shallow diffusion Reactions which occur during annealing are depths. These aspects have become particularly quite similar and are summarised below: important as device dimensions are continually (a) Palladium and platinum react with com- being decreased in size. However, it is difficult pound 111-Vs at low temperatures to form metal- to meet all the requirements in a given contact rich ternary phases. Many of these are amor- metallisation. In order to achieve low contact phous, particularly those with InP. resistance, interdiffusion between the metalli- (b) Annealing of the ternary phases results in sation components and the semiconductor is their decomposition into binary phases and/or needed and this can compromise contact elemental species. stability and uniformity. Portions of isothermal sections (at 600°C) of The electrical properties of ohmic contacts are the phase diagrams, determined kom bulk spec- defined by a specsc contact resistance, rc, (13): imens for Pd-In-P, Pt-In-P, Pd-Ga-As and Pt-Ga-As systems are shown in Figures 2 and rc = (SV/SJ)v = (Q cm') (1) 3. Note, the similarities between the systems, where V is the voltage and J is the current den- particularly the three-phase region bounded by sity. For a homogeneous contact of area A with InP or GaAs, and the binary phases with the a uniform current density, the contact resistance Group I11 and Group V elements. Annealing of R, is simply: thin palladium or platinum layers on the 111-V semiconductor should then result in the for- Rc = rcIA mation of the phases in the three phase region. The measured resistance R will be approximately equal to R, for most sample geometries when Palladium in Ohmic Contacts rc 2 1O-, R an2.For lower values of rc, the spread- Palladium can be utilised on its own to form ing resistance of the semiconductor and the ohmic contacts to 111-V semiconductors (for series resistance of the connecting wires and example, Pdln-type InP with a contact resis- semiconductor substrate must be taken into tance of 7 x 10-5 Q cm2 (1, 2)). However, pal- account. Specific contact resistances of < ladium is generally one component in a multi- R cm2 are required for ohmic behaviour, layer metallisation, where its primary functions although values in the 10-6 to lo-' Q cm2range are to serve as an adhesion layer and to initiate are most desirable. reactions with the underlying semiconductor. The annealing behaviour of a layer of palladium Platinum Metals in Ohmic Contacts (several tens of nanometres thick) on InP or Palladium and platinum are common com- GaAs plays an important role in how the con- ponents in ohmic contact metallisation schemes tact functions. to 111-V semiconductors. Many of the original In the PdInP system, see Figure 2(a), an 111-V ohmic contacts were gold-based and amorphous ternary phase (Pd=,InP) forms dur- although these contacts possess low resistance ing palladium deposition and grows on anneal- values, they are plagued by problems of stabil- ing (1 7, 18). At = 225"C, crystalline islands of ity and uniformity of interface structures. cubic PdJnP (L1 ,-type structure) begin to Platinum metals based contacts are generally nucleate and grow at the amorphous layer/InP less reactive and produce more uniform inter- interface. After annealing at 225 to 275"C, faces. Common features of the platinum met- Pd,InP grows into a continuous, epitaxial layer als include ease of deposition, good oxidation (40-50 nm thick). Two other ternary phases, resistance, relatively low reaction temperatures Pd51nP and Pd,InP(II) (of composition and with 111-V compound semiconductors (which structure similar to PdJnP) then form and also greatly enhances contact adhesion to the semi- grow epitaxially. At 300 to 350"C, all the

Platinum Metals Rev., 1999, 43, (1) 4 Fig. 2 Isothermal sections at P 600°C of ternary phase diagrams (14-16): (a) Pd-In-P (b) Pt-In-P

In w

/; I/

palladium is consumed and Pd21nP(II) is the with palladium being the dominant diffusing only phase present on InP. species. A second ternary phase, Pd,(GaAs) , For the PdGaAs system, see Figure 3(a), a forms at higher annealing temperatures (up to hexagonal ternary phase, Pd,(GaAs)*,forms and = 350°C) (19,20). This phase also demonstrates grows epitaxially on GaAs during palladium an orientation relationship with GaAs. Growth deposition (19,20). Growth of this phase con- of the ternary phases consumes the palladium tinues during subsequent annealing (c250"C), by temperatures of = 300 to 325°C.

Platinum Metah Rev., 1999, 43, (1) 5 Pd Fig. 3 Isothermal sections at (a) 600°C of ternary phase diagrams (14-16): 600'C (a) Pd-Ga-As (b) Pt-Ga-As

G AS

600.C

Ga As GaAs

Further annealing of palladium metallisations t 400°C results in decomposition of Pd21nP(II) results in decomposition of the ternary phases to PdIn and PdP, (17), which are the equilib- and subsequent formation of binary compounds. rium phases in contact with InP (Fig. 2 (a)). In the case of GaAs: PdGa and PdAs, have been reported to form in one study (19), while PdzGa Specific Contacts and Pd,As were reported in another study (20). As mentioned above, palladium can be used According to the Pd-Ga-As phase diagram, by itself in ohmic contacts, however, its use in Figure 3(a), PdGa and PdAs, are the stable this way is rare. Instead, in practice, palladium phases in contact with GaAs. is utilised as an integral component in many Annealing samples of PdhP at temperatures contacts, with its primary role being that of

Platinum Metals Rev., 1999, 43, (1) 6 an adhesion layer to the 111-V semiconductor. (for example, titanium/platinum) is needed to GelPd One particular contact structure of inter- prevent the oxidation of germanium during sub- est is Ge/Pd, which was originally applied to sequent device processing (4). Figure 4(a) shows n-type GaAs (21-24) (and later to InP, see below an image of a platinum/titanium capped sam- (3, 25)). Ohmic contact formation is based on ple, while Figure 4(b) shows contact oxidation a solid phase regrowth mechanism (21). and deterioration for an uncapped sample. The According to this mechanism, films of two ele- Ti/Pt remains inert relative to the ohmic con- ments, M and M (palladium and germanium tact until annealing above = 550"C,whereupon for this specific case) are deposited sequentially complex reactions result in rapid deterioration on a 111-V semiconductor, AB (such as GaAs). of the microstructure (26).Figure 4(c) shows At low annealing temperatures, the M metal the initial decomposition of PdGe at 550°C. film adjacent to the semiconductor reacts with PdGe-InP Similar Pd/Ge contacts have since AB to form a ternary phase M,AB: been fabricated to n-type InP (3, 25). Pd,InP

xM + AB + M,AB 4Pd + GaAs + PdrGaAs The second film (M' or Ge) is chosen so that it drives the decomposition of M,AB and forms a stable binary compound with M. M' should also be a suitable dopant for AB.

(xy)M' + M,AB + AB + xMM6 4Ge + Pd,GaAs + GaAs + 4PdGe AB regrows, doped with M, epitaxially on the AB substrate. For the Ge/Pd- GaAs system annealing temperatures are in the range 300 to 500°C. In this contact, the onset of ohmic behaviour cor- responds to the decomposition of Pd,GaAs, which is driven by inward diffusion of germanium, and results in a highly doped regrown semiconductor layer. Specific contact resistances of the order of 5 x 10.' to 1 x R cmz have been achieved for both n-type and ptype GaAs, see the Table. Selecting the cor- rect Ge:Pd ratio is crucial for fabricat- ing uniform and stable contacts: the Ge:Pd atomic ratio must slightly exceed 1. This ensures that the only stable binary phase that forms is PdGe and this pre- vents the formation of other binary phases, as and such PdzGe, pdGa' Fig. 4 TEM cross-section images of PdlGe contacts to In addition, any excess germanium is n-type GaAs: available for doping purposes. (a) with a TilPt capping layer (b) without a TiPt capping layer (4) For comprising (c) the contact in (a) has been annealed at 550°C and shows contacts to n-type GaAs, a capping layer initial decomposition of PdGe (26)

Platinum Metals Rev., 1999, 43, (1) 7 I I

Fig. 5 TEM cross-section micrographs of Ti/Pt/Au contacts top-type InGaAs (33): (a) as deposited; (b) 275°C; (c) 300°C; (d) 350°C; (e) and (f)are schematics of (a) and (d), respectively

forms initially followed by decomposition to formation begins at about 325"C, followed at PdGe and regrown InP. Contact resistances in = 350°C by the formation of a crystalline ternary the region of 1O4 R cm2have been achieved, see phase (PtJnP) (27). PtJnP does not form at the Table. the amorphous layer/semiconductor interface, but at the amorphous layerimetallisation inter- Platinum in Ohmic Contacts face, and as such exhibits no preferred orien- Reactions for the PtlInP system are similar tation with the InP substrate. This is in contrast to those for the PdInP system. The main dif- to Pd/InP where crystalline ternary phases nucle- ference is that the reaction temperatures tend ate, and then grow with a preferred orientation, to be higher for platinum, which is not sur- at the semiconductor surface. A second ternary prising as platinum has a higher melting point phase forms at 400°C which is followed by than palladium. Ternary amorphous phase decomposition of both ternary phases to binary

Platinum Metals Rev., 1999, 43, (1) 8 phases at temperatures higher than 450°C. The final phases are Pan, and PtP,, which agree with those expected from the bulk Pt-In-P phase diagram, see Figure 2 (b) (14, 28). Pt/GaAs reactions, see Figure 3(b), are similar to those of Pt/InP, with PtAs, and PtGa binary phases forming at temperatures = 550°C (29-31). Non-Alloyed Contacts The main application of platinum in ohmic contacts to 111-V semiconductors (including InGaAs and InGaAsP) is in the so-called non-alloyed contacts. These usually consist of titanium and platinum layers, with or without a gold capping layer, deposited sequentially on the semiconductor (7, 8, 32). Gold, which can be deposited either before or after contact annealing, is needed to permit wire bonding and solder bonding of the device to a suitable submount. Deposition of gold prior to annealing permits deposition of all the metal layers in one sequence, without breaking the vacuum, although gold may reduce contact stability during subsequent annealing. The titanium layer improves adhesion to the underlying semiconductor, while the platinum layer acts as a diffusion barrier for gold. Good contacts to a number of semiconductors have Fig. 6 TEM plan view images of indium particles at been obtained using this scheme, see the Table, the TinnGaAs interface (33): giving contact resistance values depending very (a) 275°C and (b) 350°C much on the initial doping levels in the semiconductors. The original doping levels in the relative to InP (E, = 1.35 eV) and high dopant semiconductors are generally quite high, so that solubility (= IOl9 cm-’ for zinc) permit the many of these contacts are ohmic without being formation of low resistance contacts. Specific annealed or require very little annealing to attain contact resistances as low as 3 x 10-8 R cm2(for ohmic behaviour, hence, the term non-alloyed high doping levels) have been reported, see the contacts. Table. In reality, many of these contacts are annealed A series of TEM cross-section micrographs, to optimise the electrical properties and there- showing microstructure development during fore undergo fairly significant interfacial reac- annealing are shown in Figure 5 (33).Reaction tions, making the terminology “non-alloyed” between titanium and InGaAs begins at = 275°C something of a misnomer. An example of one and shows up as small dark contrast features of these contacts to p-type InP, and the inter- ’at the Ti/InGaAs interface, Figure 5(b). These facial reactions involved, is discussed below. have been identified as metallic indium parti- TilPtlAu is the standard p-side metallisation cles, which nucleate uniformly across the used for a number of InP-based laser and opti- TflnGaAs interface and grow to = 100 nm in cal wave-guide devices. pType InGaAs is grown size, see Figures 5(c) and 5(d). The indium par- as a lattice matched capping layer (In,s,Gao 47A~)ticles are pyramidal in shape and grow along on InP. Its low band gap (E, = 0.75 eV) low energy { 1 10) and { 1 1 1} planes, Figures

Platinum Metals Rev., 1999, 43, (1) 9 ,\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ Pd

PtASz YflXA m PdGa GaAs

Fig. 7 TEM cross-section images and related schematics of PdPtlAuPd contact to an InGaPlGaAs heterojunction bipolar transistor (5): I (a) as deposited and (b) annealed at 440°C

5(d) and 6. Indium is a low melting point metal Some metallisations incorporate both palla- (157"C), which can dissolve up to = 1.4 weight dium and platinum. One exa'mple was given per cent gallium and up to = 1 weight per cent previously (Pd/Ge/Ti/Pt to n-type GaAs, in zinc (the dopant in InGaAs). Both the gallium Figure 4(a)), although the platinum was essen- and zinc impurities lower the melting point of tially inert and acted solely as a capping layer. indium, which can affect the long term stabil- However, in some instances, both palladium ity of devices. TiAs also forms at the Ti/InGaAs and platinum participate in metallisatiodsemi- interface and thickens with increasing anneal- conductor reactions. This is shown in both ing temperature, see Figure 5(d). Depletion of Figures 7(a) and 7(b) for a multilayer pcontact indium and arsenic from the InGaAs layers PdPtlAulPd, utilised for InGaP/GaAs het- results in the formation of gallium-rich InGaAs. erojunction bipolar transistors (HBT) (5). The Platinum is an effective barrier, preventing metal layers are deposited directly onto the emit- inward diffusion of gold and outward diffu- ter layer (InGaP) of the HBT, with palladium sion of the Group I11 elements (indium and gal- and platinum reacting with and consuming the lium), up to annealing temperatures of 450°C. InGaP during annealing to form an ohmic At higher temperature significant interdiffusion contact with the underlying base material (p- between titanium and platinum occurs. type GaAs). Lateral uniformity is particularly

Platinum Metals Rev., 1999,43, (1) 10 important because of the thin nature of the base PtAs, and PdGa, see Figure 7 (b). In this layer (< 100 nm). An outer layer of palladium structure, contact resistance values < 10” R cm’ protects the gold during subsequent device pro- are attainable. cessing; dry etching sputters the gold but not the palladium. The doping level in the base layer Summary is high enough (> loL9~m-~) that additional Platinum and palladium are common dopant is not required to achieve low contact components in ohmic contacts to 111-V semi- resistances. The initial reaction between palla- conductors. The metals react readily with the dium and platinum and InGaP results in the semiconductor at relatively low temperatures, formation of a 5-component amorphous layer forming ternary phases initially, followed by (Pd, Pt, In, Ga and P), which crystallises binary phase formation. Palladium is utilised to (Pt,Pd,~,),(In,Ga,.,)P (0 Ix, y I 1) at the primarily as an adhesion layer to the semicon- Pdamorphous layer interface. Annealing at tem- ductor, while the major role of platinum is as peratures 2 415°C results in the complete con- a diffusion barrier. In both cases, palladium and sumption of InGaP and partial decomposition of platinum act to improve contact stability and the GaAs base layer, resulting in a relatively uni- hence the reliability of the device to which they form contact consisting of (PtxPdl,) (In,Ga ,-,) P, are attached.

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Platinum Metals Rev., 1999, 43, (1) 11 29 T. Sands, V. G. Keramidas, A. J. Yu, K. M. Yu, R. 32 D. G. Ivey, P. Jian, R. Bruce and G. Knight, Gruns!y and J. WashbumJ Marer. Res., 1987,2,262 J. Mater. Sci. :Mater. Electron., 1995, 6, 2 19 30 V. Kumar,J. Phys. Chem. Solids, 1975, 36, 535 31 C.Fontaine, T. Okumura and K. N. Tu,J. Appl. 33 D. G.Ivey, S. Ingrey, J.-P. Noel and W. M. Lau, Phys.,1983, 54, 1404 Mater. Sci. Eng., 1997, B49, 66 Platinum Dve Used in Electroluminescent Devices J Electroluminescent devices (LEDs) convert ciencies by using a phosphorescent dye in the electricity to light and are increasingly used semiconductorhost (M. A. Baldo, D. F. O’Brien, in, for example, flat-panel displays. They are Y. You, A. Shoustikov, S. Sibley, M. E. usually made by sandwiching a layer of semi- Thompson and S. R. Forrest, “Highly Efficient conductor between one electrode with a high Phosphorescent Emission from Organic work function (a source of holes) and an elec- Electroluminescent Devices”, Nature, 1998, trode with a low work function (an electron 395, (6698), 151-154). The phosphorescent source). In the presence of an applied electric dye, 2,3,7,8,12,13,17,18-octaethyl-2lH,23H- field an electron-hole exciton is formed (both porphine platinum(I1) (PtOEP), enables both singlet and mplet states) and the radiative recom- singlet and triplet exciton states to be used in bination of the (singlet) exciton generates a pho- the light-emission process, and external energy ton that re-appears as visible light emitted from conversion efficiencies of up to 4 per cent have the device. been achieved. The current trend is towards the development PtOEP is relatively well-known as a red- of polymeric electroluminescent material emitting phosphorescent dye and in comparison because of the processing advantages. There is with other compounds with saturated red-emis- also a need to improve the overall energy con- sion, PtOEP possesses quantum and power effi- version efficiency of LEDs, which is typically of ciencies that are superior by at least an order of the order of 1 per cent. One approach to the lat- magnitude. The presence of the heavy platinum ter problem has been to introduce lumines- atom in the porphine ring increases the spin- cent dyes into the host semiconductor mater- orbit coupling of the molecule, the triplet state ial. Provided that the absorption spectrum of gains additional singlet character and vice versa. the dye overlaps well with the emission spec- This also enhances the efficiency of intersystem trum of the host material, efficient energy-trans- crossing from the first singlet excited state to the fer from the host to the dye can occur. However, triplet excited state. Thus the enhanced phos- only the singlet exciton states (approximately phorescent light emission from the PtOEP adds 25 per cent of the total) can be used in the addi- significantly to the overall light-emitting process tional fluorescent emission. in the LED. The work also establishes the utility Now, workers from Princeton University and of PtOEP as a probe of triplet behaviour and the University of Southern California have energy-transfer in organic solid-state systems. demonstrated improved light emission effi- R. J. POlTER International Symposium on Iridium There will be an International Symposium on ings of the symposium will be published. Iridium held at the Annual Meeting of The Evan Ohriner of Oak Ridge National Laboratory Minerals, Metals and Materials Society (TMS) is the Primary Organiser of the Symposium; H. in Nashville, Tennessee, U.S.A., from March Harada, National Research Institute for Metals, 1lth to 17th, 2000. Japan; R. D. Lanam, Engelhard-CLAL, U.S.A. The symposium will address all aspects of the and P. Panfilov, Ural State University, metallurgy, production, and applications for Ekaterinburg, Russia are the co-organisers. iridium and iridium-containing materials. Abstracts of papers should be submitted by Particular attention will be given to refining and June 15th 1999 to http://www.tms.org/cms., recycling; processing iridium compounds; the or contact the Primary Organiser: E. K. Ohriner, processing, structure, and properties of iridium Oak Ridge National Laboratory, P.O. Box 2008, and its alloys; iridium coating technology; com- MS 6083, Bldg. 4508, Oak Ridge, TN ponent design and applications and iridium as 3783 1-6083, U.S.A.; telephone: +1-(423)- an alloying element in metallic and intermetal- 574-8519; fax: +1-(423) 574-4357; e-mail: lic systems. It is anticipated that the proceed- [email protected].

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