Herbert D. Kaesz

Focused ion beam induced deposition of platinum

Focused ion beam induced deposition of platinum from a precursor gas of (methylcyclopentadienyl)trimethyl platinum has been demonstrated. This organometallic compound is solid at room temperature with a vapor pressure of 0.054 Torr. Ga+ ions at 30–40 keV have been used. The resistivity and composition of the film and the deposition yield have been measured as a function of ion current density, line dose, substrate temperature, geometry, and supplemental hydrogen pressure. Yield varies from 0.2 to 34, and resistivity varies from 70 to 700 μΩ cm depending on the conditions. The resistivity and content of the carbon impurity are reduced as the ion current increases: the lowest resistivity is observed at the highest current density corresponding to 0.222 nA at scan speed 500 cm/s repeated over a 350 μm long line. The minimum linewidth achieved so far is 0.3 μm. Transmission electron microscopy shows the Pt film to be amorphous, and Auger analysis gives the film composition 46% Pt, 24% C, 28% Ga, and 2% O. The...

Proton magnetic resonance and infrared spectral parameters for the tin-hydrogen bond in some alkyl- and phenylstannanes

Abstract The possibility of donor-acceptor interaction between amines or phosphines and stannane or the alkylstannanes is investigated by proton magnetic resonance; present evidence is in the negative for a strong interaction. A correlation between Sn-H coupling constant and Sn-H stretching frequency and the properties of alkyl groups in alkylstannanes is proposed.

Synthesis, spectroscopic characterization and crystal and molecular structure of HRu3(OCN(CH3)2)(CO)10

Abstract Dimethylamine reacts with Ru3(CO)12 to produce the η2-hydrido-η-formamido cluster complex HRu(OCN(CH3)2)(CO)10 (I). This formulation is consistent with spectroscopic features such as the absence of v(NH) in the infrared, the presence in the Raman of v(RuHRu) at 1400 cm−1 (v(RuDRu) at 990 cm−1) and indication in the 1H NMR of diastereotopic methyl groups bonded to the nitrogen atom. Since these data could not lead to an unequivocal structure assignment a single crystal X-ray study at 115 K was undertaken. The complex crystallizes in the triclinic space group, P 1 with cell dimensions; a 7.299(33) », b 9.5037(40) », c 13.7454(57) », α 91.876(34)°, β 96.387(34)°, γ 95.341(34)° and Z = 2. The structure was solved by a combination of Patterson and Fourier techniques and refined by full matrix least squares to a final R = 0.054 and Rω = 0.074 for 3074 unique reflections. The three ruthenium atoms define a triangle of unequal sides with both the hydride and formamido groups bridging the longest edge; the formamido group is coordinated through the carbon and oxygen atoms. The edge of the ruthenium triangle bridged both by the hydrogen atom and the formamido group is 2.8755(15) »; the other two edges of the ruthenium triangle are observed to be 2.8319(15) and 2.8577(14) », respectively. In the formamido group the distance CO 1.287(9) » and CN 1.340(10) » reflect partial double bond charater in each bond consistent with observation of two chemically distinct methyl groups on the dinitrogen atom. The hydrogen atom bridging one edge of the ruthenium triangle is asymmetrically positioned at 1.73(9) » from the ruthenium atom bonded to the oxygen atom and 1.91(9) » from the ruthenium atom bonded to the carbon atom of the carboxamido group.

Low‐temperature organometallic chemical vapor deposition of platinum

Impurity‐free, polycrystalline films of platinum have been grown by the decomposition of cyclopentadienyl platinum trimethyl, CpPtMe3, in hydrogen and a noble gas over silicon or glass substrates heated to 180 °C. The films contain less than 1 at. % of oxygen and carbon, and no other detectable impurities, as measured by x‐ray photoelectron and Auger spectroscopies after argon ion sputtering. Sheet resistivities are 50% greater than sputter‐deposited platinum.

Chemical vapor deposition of CoGa and PtGa2 thin films from mixed‐metalorganometallic compounds

A new process for deposition of thin metal films from organometallic precursors of limited volatility has been demonstrated. Short path vapor transport of the complexes dichloro(tetracarbonylcobalt)gallium(III) tetrahydrofuranate, (CO)4CoGaCl2(THF), or platinum(bis‐dimethylglyoximato)(bis‐dimethylgallium), Pt{(N2C2(CH3)2O2)(GaMe2)}2, each under a stream of hydrogen, leads to the films of the intermetallic compounds CoGa and PtGa2, respectively, on substrates such as Si (100) wafer or a glass slide at 500 °C. The compounds were identified and characterized by x‐ray diffraction, Auger electron and x‐ray photoelectron spectroscopies. The films are crystalline and highly reflective. The CoGa film is single phased; the PtGa2 film shows a minor constituent of Pt2Ga3.

Organometallic chemical vapor deposition of tungsten metal, and suppression of carbon incorporation by codeposition of platinum

Highly reflecting, amorphous, thin films of tungsten are obtained by the decomposition of bis‐cyclopentadienyltungstendihydride, (η‐C5H5)2WH2, in 1 atm of hydrogen at 350 °C. Auger depth profiling reveals that the carbon and oxygen content of the films are 25.1 and 3.1 at. %, respectively. Simultaneous chemical vapor deposition of tungsten with a small amount of platinum reduces the carbon and oxygen content of the film to 5.3 and 1.8 at. %. The platinum is deposited from cyclopentadienylplatinumtrimethyl, (η‐C5H5)Pt(CH3)3, and its concen‐ tration in the film is 3.3%. Annealing at 750 °C in hydrogen converts the tungsten into a polycrystalline deposit which exhibits an x‐ray diffraction pattern characteristic of the metal. The sheet resistivities of the amorphous films are 52±4 μΩ cm.Highly reflecting, amorphous, thin films of tungsten are obtained by the decomposition of bis‐cyclopentadienyltungstendihydride, (η‐C5H5)2WH2, in 1 atm of hydrogen at 350 °C. Auger depth profiling reveals that the carbon and oxygen content of the films are 25.1 and 3.1 at. %, respectively. Simultaneous chemical vapor deposition of tungsten with a small amount of platinum reduces the carbon and oxygen content of the film to 5.3 and 1.8 at. %. The platinum is deposited from cyclopentadienylplatinumtrimethyl, (η‐C5H5)Pt(CH3)3, and its concen‐ tration in the film is 3.3%. Annealing at 750 °C in hydrogen converts the tungsten into a polycrystalline deposit which exhibits an x‐ray diffraction pattern characteristic of the metal. The sheet resistivities of the amorphous films are 52±4 μΩ cm.

Reversible syntheses of mono-(cyclopentadienyl)rhodium-tri-ruthenium cluster complexes and (η-C5Me5)2Rh2Ru2(CO)7; crystal and molecular structures of CpRhRu3{μ-H}2{μ-CO}(CO)9, Cp = η-C5H5 or η-C5Me5 and (η-C5Me5)Rh{μ-H}2Ru3{μ-H}2(CO)9

Abstract The mixed metal complexes CpRhRu 3 {μ-H} 2 {μ-CO}(CO) 9 , ( 3a : Cp = η-C 5 H 5 ; 3b : Cp = η-C 5 Me 5 ) 4b : (η-C 5 Me 5 )RhRu 3 {μ-H} 4 (CO) 9 , 5 : (η-C 5 Me 5 ) 2 Rh 2 Ru 2 (CO) 7 ) are formed when H 2 is bubbled through solutions of Ru 3 (CO) 12 and the respective CpRh(CO) 2 at 70–90°C. These are easily disrupted at 25°C back into the starting materials under an atmosphere of CO. Using 13 CO, the starting materials are obtained with complete 13 CO exchange. While CpRh(CO) 2 undergoes exchange at 25°C with 13 CO at atmospheric pressure, Ru 3 (CO) 12 does not, nor does it exchange in the presence of simply an added amount of CpRh(CO) 2 . Attachment of the CpRh moiety to the Ru 3 skeleton as in the products obtained in this work thus leads, under 13 CO, to the completely enriched starting materials Ru 3 ( 13 CO) 12 and CpRh( 13 CO) 2 . Structures of three new products have been determined using a Picker (FACS-1) four circle automated diffractometer and graphite-monochromatized Mo- K α radiation. For 3a , 3831 unique reflections with I > 3σ( I ) were used in the refinement; final discrepancy indices, R = 0.030 and R w = 0.050. Complex 3a crystallizes in the monoclinic space group P 2 1 / n ; cell dimensions a 8.1856(5), b 15.0706(10), c 16.3013(12) A, and β 91.033(1)°; calculated density 2.49 g cm −3 . For 3b , 4801 unique reflections with I > 3σ( I ) were used in the refinement; final discrepancy indices, R = 0.026 and R w = 0.042. Complex 3b crystallizes in the monoclinic space group P 2 1 / n in a cell having the dimensions of a 8.7580(5), b 14.5578(8), c 19.829(1) A, and β 97.591(2)°; calculated density 2.18 g cm −3 . For 4b , 6756 unique reflections with I > 3σ( I ) were used in the refinement; final discrepancy indices, R = 0.030 and R w = 0.040. Complex 4b crystallizes in the monoclinic space group P 2 1 / a ; cell dimensions a 17.470(1), b 18.451(1), c 17.200(1) A, and β 114.684(1)°; calculated density 2.10 g cm −3 . Metal atoms in all three structures were located by direct methods (MULTAN80). All other nonhydrogen atoms were then located by difference maps. Hydrogen atoms bridging various edges of the clusters were located after all hydrogen atoms in the η-C 5 H 5 (= Cp) or η-C 5 (CH 3 ) 5 (= Cp★) groups were refined isotropically in calculated positions. Each of the crystals studied consists of discrete molecules of the complexes, each with a triangle of ruthenium atoms capped by a CpRh or Cp★Rh group. Isomeric structures are observed for 3a and 3b . In the former, a CO group is found bridging between one Ru atom and the Rh atom while one each of two cluster-bound hydrogen atoms bridge two separate edges of the Ru 3 triangle. In 3b , both a CO group and one of the cluster-bound hydrogen atoms are found bridging between Rh and two separate Ru atoms of the Ru 3 triangle. The remaining cluster-bonded hydrogen atom is found bridging one edge of the Ru 3 triangle. In 4b , two of the cluster-bound hydrogen atoms are found (one each) on two edges of the Ru 3 triangle. The other two are found bridging each of two of the RuRh bonds. The metal—metal separations in the three structures are summarized as follows. Unbridged RuRu and RhRu fall in the ranges 2.765(1) to 2.813(1) A and 2.707(1) to 2.752(1) A, respectively; the Rh-μ-(CO)-Ru separations are 2.727(1) (in 3a ) and 2.7515(1) (in 3b ). Ru-μ-(H)-Ru separations fall in the range 2.870(1) to 2.938(1) A while Rh-μ-(H)-Ru fall in the range 2.871(1) to 2.9169(1) A.

Investigation of [(py) (Et) Co(dmg · GaEt2)2] and [Ni(dmg · GaEt2)2] (py = pyridine; dmg = dimethylglyoximato) as single source precursors for deposition of β-CoGa and NiGa by MOCVD. Crystal structure of [(py)(Et)Co(dmg · GaEt2)(dmgH)]

Abstract The complexes [(py)(Et)Co(dmg · GaEt 2 ) 2 ], 1 , and [Ni(dmg · GaEt 2 ) 2 ], 2 , (dmg = dimethylglyoxime) were synthesized for study as potential precursors for Metalorganic Chemical Vapor Deposition (MOCVD) of β-CoGa and NiGa. Complex 1 is easily hydrolyzed to [(py)(Et)Co(dmgH)(dmg · GaEt 2 )], 3 ; a single crystal X-ray structure was obtained for this product. Thermogravimetric analyses (TGA) under H 2 flow resulted in a residual mass of 35% at 650°C for 1 (residual for CoGa 2 is 31%) and 29% at 500°C for 2 (residual for NiGa 2 is 36%). The highest peaks in the electron impact MS corresponded to (MWt  py  2C 2 H 5 ) + , 1 , and (MWt  C 2 H 5 ) + , 2 . The next peaks for both compounds corresponded to loss of the remaining ethyl groups. MOCVD at 560°C resulted in polycrystalline β-CoGa (using 1 as a precursor) and polycrystalline NiGa ( 2 ). Upon raising the temperature of the GaAs substrate to 630°C, 1 gave films with areas of epitaxial growth in a primarily polycrystalline β-CoGa film; partial degradation of the substrate also occurs. EDS and XPS data showed how film composition can be controlled by precursor design. EDS analysis of the CoGa (1 : 2.4) and NiGa (1 : 2.0) films showed that stoichiometry of the precursors was principally retained. The films exhibit only negligible carbon or nitrogen contamination, but the oxygen content is relatively high (10–20%). XPS data show that oxygen near the surface is bonded to both Co and Ga, but in the film, oxygen is only bonded to Ga.

Scanning tunneling microscopy study of platinum deposited on graphite by metalorganic chemical vapor deposition

Abstract The growth of thin Pt(111) films on highly oriented pyrolytic graphite (HOPG) by metalorganic chemical vapor deposition has been followed by scanning tunneling microscopy. Depositions were carried out on substrates held at 205°C and contacted with intersecting streams of H 2 and of He saturated with (η 5 −C 5 H 4 CH 3 )Pt(CH 3 ) 3 . The deposition was monitored by the appearance methane in the product stream. Deposition initiated almost immediately, in contrast with earlier studies showing a significant induction period for deposition on glass. The deposits obtained after several minutes at 205°C consisted of Pt clusters with diameters ranging from 8 to 80 A along with some very much larger Pt islands. The deposits were morphologically very rough with rather well defined facet orientation. The step heights of the terraces ranged from 20 to 54 A. Oval shaped disks free of apparent dislocations were also observed. One of the larger crystallites investigated was 2074 × 1482 A 2 and 200 A in height. The deposits were non-uniform throughout the deposition. The initial crystal growth under CVD was by island nucleation, followed by a growth mode that produced a random rough surface after the islands coalesced. At early stages the films are preferentially oriented with (111) crystallites parallel to the HOPG basal plane; further growth, however, leads to a poly-crystalline deposit.

Study of CoGa deposition from the single source precursor (CO)4CoGaCl2 (THF)

Abstract Depositions of thin films of CoGa from the single-source precursor (CO)4CoGaCl2(THF) (1) have been carried out in an epitaxial organometallic chemical vapor deposition reactor. Prior to deposition, mass spectrometric (MS) and thermogravimetric (TGA) analyses of 1 were undertaken. Electron impact MS reveals a tendency for 1 partially to disproportionate (after loss of THF) into ClGa[(CoCO)4]2 and GaCl3 at probe temperature (120°C). The parent molecular ion for 1 appears with only low relative intensity (1%) indicating easy loss of THF as the first step. The principal features of the spectrum can be assigned to step-wise CO-loss series of peaks derived from three parent ions [(CO)4CoGaCl2]+ (a), [(CO)4CoGaCl]+ (b), and [(CO)4Co]+ (c). The relatively high intensity of the peaks derived from parent ions (a) and (b) indicate a relatively good stability of the CoGa bond through to the species [CoGa]+ (rel. int. 15%). TGA of 1 under Ar shows decomposition in a single step in the range 100 to 230°C; residual weight of 44% is higher than expected for CoGa alone. Under H2 however, a multistep decomposition process is observed culminating at 400–450°C; residual weight is 33%, close to that expected for CoGA. In the (cold wall) CVD reactor, optimum deposition occurs under reduced pressure (0.9–6 torr) and laminar flow conditions using H2 as carrier gas for (100)GaAs, (100)Si, and Al2O3 as substrates; growth rates are about 1.8 μm/h. Polycrystalline films are obtained under all conditions; annealing under H2 for 2 h at 500°C gives relatively sharp XRD patterns for β-CoGa. For depositions in the range 250 to 350°C the Co/Ga ratio in the films is close to 1/1 showing control of stoichiometry by the precursor. These films however still contain some Cl. In the range 350 to 400°C the Cl content is lowered, however, the films become Co rich indicating loss of Cl is accompanied by loss of Ga. The stoichiometric control achieved in the present work indicates that single source precursors of ratio CoGa2 could give Ga rich (64 at.% Ga) β-cubic CoGa for lattice matching to (100)GaAs.