Evaporation of Cu

Reactive sputtering in an argon-H2S-mixture leads to a defined deposition of the Cu S layer. The reaction occurs apparently at the substrate. By variation of the partial pressure of H2S the stoichiometry of Cu S can be controlled. Sputtering rates of 6 ym/h at substrate temperatures between 100 and 150 have been indicated /22,23/. Problems arise from the fact that different phases of Cu S exist. The electrical resistivity and the Cu S ratio as a function of the H2S partial pressure during sputtering are shown in figure 6. At low pressure a precipation of pure Cu and the formation of Cu cones was observed. In this Cu rich phase the electrical resistivity increases obviously to very high values. 

Partial pressures above the limits in figure 6 lead to sulfur rich phases of Cu S. The CUj S films sputtered on CdS films exhibited epitaxial growth as demonstrated by Armantrout et al. /22/ by electron diffraction and hence showed no higher recombination velocity at the interface than in topotacially grown junction layers. 

From all methods in Cu S film preparation the dipping process is the one which is most frequently applied. Other methods which are based on Cu deposition, by evaporation or by electrochemical 

The CdS layer acts as a collector for the electrons from CUxS during solar cell operation. Furthermore it serves generally as the basis for the topotaxial formation of the Cu S layer. Hence the crystalline structure and the electrical properties of the film are of major interest. The physical properties of the CdS films reported in the following sections are characteristic to films with optimum photovoltaic efficiency. 

---

Coppet(II) oxide [1317-38-0] CuO, is found in nature as the black triclinic tenorite [1317-92-6] or the cubic or tetrahedral paramelaconite [71276-37 ]. Commercially available copper(II) oxide is generally black and dense although a brown material of low bulk density can be prepared by decomposition of the carbonate or hydroxide at around 300°C, or by the hydrolysis of hot copper salt solutions with sodium hydroxide. The black product of commerce is most often prepared by evaporation of Cu(NH2)4C02 solutions (35) or by precipitation of copper(II) oxide from hot ammonia solutions by addition of sodium hydroxide. An extremely fine (10—20 nm) copper(II) oxide has been prepared for use as a precursor in superconductors (36). 

Fig. 4.46 Lateral composition profile obtained for a Ni-5% Cu annealed at 550°C. The first few ions detected are Cu. This may indicate an edge effect, or simply preferential field evaporation of Cu from plane edges of Cu atoms.

Some interesting features can be noticed in these lateral concentration profiles and composition depth profiles. For the Ni-5% Cu alloy, the first few ions detected are Cu ions, even though the composition within the top layer is rather uniform. This can be due to an edge effect, in other words the edges of the (111) layers are much more enriched with Cu atoms than inside the top (111) layer. This can also be simply produced by a preferential field evaporation of Cu atoms from the layer edges. While... 

Spherical precipitates in the skin of a polymer have previously been observed after the evaporation of Cu on polyimide(PI)(liD- These two systems [Al/PET(sample(l)) and Cu/PI] present a low chemical interaction and a low adhesion, but the deposition rate was much lower for Cu/PI than for Al/PET (1 ML/mn compared with 50 nm/s). This behaviour has been interpreted by Le Goues and alfl 01 as a consequence of a poor chemical interaction between the metal and the polymer at the interface the metal being free to diffuse in the polymer to form clusters of nearly spherical shape. However, it is difficult to compare the mechanism of formation of these precipitates because of the huge evaporation rate difference this rate seems to be critical (Le Goues and al(l Oil for the formation of these precipitates. The presence of these precipitates can only be considered as a fingerprint of a poor quality interface. 

In a typical experiment 105 mg (0.50 mmol) of 3.8c, dissolved in a minimal amount of ethanol, and 100 mg (1.50 mmol) of 3.9 were added to a solution of 1.21g (5 mmol) of Cu(N03)2 BH20 and 5 mmol of ligand in 500 ml of water in a 500 ml flask. -Amino-acid containing solutions required addition of one equivalent of sodium hydroxide. When necessary, the pH was adjusted to a value of 5 ( -amino acids) and 7.5 (amines). The flask was sealed carefully and the solution was stirred for 2A hours, followed by extraction with ether. After drying over sodium sulfate the ether was evaporated. Tire endo-exo ratios were determined from the H-NMR spectra of the product mixtures as described in Chapter 2. 

In a typical procedure, a solution of 0.175 mmol of L- -amino acid and 0.175 mmol of NaOH in 1 ml of water was added to a solution of 0.100 mmol of Cu(N03)2in 100 ml of water in a 100 ml flask. Tire pH was adjusted to 6.0-6.5. The catalyst solution was cooled to 0 C and a solution of 1.0 mmol of 3.8c in a minimal amount of ethanol was added, together with 2.4 mmol of 3.9. The flask was sealed carefully. After 48 hours of stirring at 0 C the reaction mixture was extracted with ether, affording 3.10c in quantitative yield After evaporation of the ether from the water layer (rotary evaporator) the catalyst solution can be reused without a significant decrease in enantioselectivity. 

Examples of this procedure for dilute solutions of copper, silicon and aluminium shows the widely different behaviour of these elements. The vapour pressures of the pure metals are 1.14 x 10, 8.63 x 10 and 1.51 x 10 amios at 1873 K, and the activity coefficients in solution in liquid iron are 8.0, 7 X 10 and 3 X 10 respectively. There are therefore two elements of relatively high and similar vapour pressures, Cu and Al, and two elements of approximately equal activity coefficients but widely differing vapour pressures. Si and Al. The right-hand side of the depletion equation has the values 1.89, 1.88 X 10- , and 1.44 X 10 respectively, and we may conclude that there will be depletion of copper only, widr insignificant evaporation of silicon and aluminium. The data for the boundaty layer were taken as 5 x lO cm s for the diffusion coefficient, and 10 cm for the boundary layer thickness in liquid iron. 

A procedure involving (a) the deposition of nearly stoichiometric films of copper and indium on suitable substrates using vacuum evaporation or electrodeposition and (b) the heat treatment of Cu-In films in a hydrogen-selenium atmosphere at temperatures above 630 °C was reported to yield large grain (several mm in size), stoichiometric thin films of chalcopyrite CIS with a preferred 112 orientation [167]. 

According to the data in Table III, the value of the ratio P)Mm is approximately the same for the metals Au, Fe, Co, Ni, and Pd. Binary alloys formed from any pair of these metals can therefore be expected to evaporate without substantial fractionation. On the other hand, films evaporated from Ag-Pd and Cu-Ni alloys can be expected to be enriched in Ag and Cu, respectively. These predictions are largely confirmed by experiment. For example, the composition of Pd-Au films was found to be the same as the wires which were evaporated (46), but in the case of Pd-Ag, evaporation of a 30% Ag-Pd alloy ware yielded a 50% Ag-Pd alloy film (47)- Alexander and Russell evaporated a number of alloys from pellets in the reaction vessel as shown in Fig. 5 (48) The alloy pellet was placed in a small quartz cup with its surface equidistant from the hemispherical top of the reaction vessel. The pellet was evaporated by... 

Alloy films are commonly sintered during preparation by deposition on substrates heated to, say, 400°C or by subsequent annealing at such temperatures, and, consequently, rather small surface areas have to be measured, perhaps in vessels of substantial volume. Krypton adsorption at liquid nitrogen temperature was used with induction-evaporated Cu-Ni, Fe-Ni, and Pd-Ni films, and BET surface areas of 1000-2000 cm2 were recorded (48), after correction for bare glass. The total area of Cu-Ni films was measured by the physical adsorption of xenon at — 196°C (70) in addition, the chemisorption of hydrogen on the same samples enabled the quantity a to be determined where... 

Further progress in the study of the Cu-Ni system awaited the preparation and careful characterization of alloy films of known bulk and surface composition. The essential step was taken by Sachtler and his co-workers 28, 88, 114) who prepared Cu-Ni alloy films by successive evaporation of the component metals in UHV. After evaporation the films were homogenized by heating in vacuum at 200°C. The bulk composition of the alloys was derived from X-ray diffraction, and the photoelectric work function of the films was also measured. A thermodynamic analysis, summarized by Fig. 13, indicated that alloy films sintered at 200°C should consist, at equilibrium, of two phases, viz., phase I containing 80% Cu and phase II containing 2% Cu. Evidence was presented that alloys within the... 

The electrolyte volume of the STM cells is usually very small (of the order of a 100 pi in the above described case) and evaporation of the solution can create problems in long-term experiments. Miniature reference electrodes have been described in the literature [36], For most metal deposition studies, a simple metal wire, immersed directly into the metal ion containing solution, is a convenient, low-noise reference electrode. This is particularly true for Cu- and Ag-deposition studies. 

Double-sided electrolytic contacts are favorable for this method of diffusion length measurement because they are transparent and the required SCRs are easily induced by application of a reverse bias. Therefore homogeneously doped wafers need no additional preparation, such as evaporation of metal contacts or diffusion doping, to produce a p-n junction. Furthermore, a record low value of surface recombination velocity has been measured for silicon surfaces in contact with an HF electrolyte at OCP [Yal], Note that this OCP value cannot be further decreased by a forward bias at the frontside, because any potential other than OCP has been found to increase the surface recombination velocity, as shown in Fig. 3.2. Note that contaminations in the HF electrolyte, such as Cu, may significantly increase the surface recombination velocity. This effect has been used to detect trace levels (20 ppt) of Cu in HF [Re5j. 

A comparison was made between Ni and Co diffusion barriers produced by electroless, electro-, and evaporation deposition (64). This comparison shows that only electrolessly deposited metals and alloys, at a thickness of 1000 im, have barrier properties for Cu diffusion. For Co(P) 1000-pm-thick barriers, annealed for 14h, the amount of Cu interdiffused into Co(P) is less than 1 at %. Thicker barriers of Ni(P), Ni(B), and Co(B) are required for the same degree of Cu interdiffusion. The same metals, if electrodeposited, both do and do not have inferior barrier properties. This... 

O- and S-donor ligands. [Tl2Cu(C03)2] has been reported. Isothermal evaporation of a solution of CuSO and CsSO at 80°C gives [Cs3Cu2(OH)2-(S04)3],2H20. The reaction of HCIO with Cu(OAc)2 in acetic acid shows the equilibria... 

A solution prepared by dissolving 0.96 g of [Cu(tpa)(0H2)][C104]2 (1-7 mmol) in 20 mL of water is stirred, and the pH is adjusted to pH 7 using 0.5 M sodium hydroxide solution. A solution of 92 mg of K3[Fe(CN)6] (0.28 mmol) dissolved in 8 mL of water is then added dropwise to the stirred solution. This resulted in the immediate formation of a purple precipitate that was collected by filtration washed successively with cold water, ethanol, and ether and then air-dried to afford a purple powder of [ Cu(tpa)(CN) 6Fe][C104]g 3H2O (Yield 0.66 g, 74%). Small dark purple crystals suitable for X-ray structure determination were obtained by slow evaporation of a solution prepared by dissolving the purple powder in hot water. 

The reaction between K[CpFe(CO)(CN)2] (0.4 mmol, 0.096 g) and [Cu(CH3CN)3][BF4] (0.4 mmol, 0.126 g) is carried out directly in dichloro-methane for 30 min, then the solution is filtered to remove the KBF4 precipitate. A solution of dcpp (0.4 mmol, 0.174 g) in 10 mL of dichloromethane is added dropwise to the yellow filtrate, and the resulting yellow solution is stirred at room temperature for 30 min. Evaporation of the solvent under vacuum provides the product as a yellow powder in 91% yield. Yellow crystals are obtained on slow diffusion of hexanes into a TFfF solution of CpFe(CO)(/r-CN)2Cu(dcpp) 2 maintained at 10°C for several days. 

Further diode measurements have been made by Culver, Pritchard, and Tompkins (77) for the adsorption of H and CO on evaporated metal films of Cu, Ag, Au and Fe, Co, and Ni. The S.P. data obtained at —183° were ... 

The salen-H4 (150 mg, 0.55 mmol) was treated with Cu(OAc)2 IH2O (200 mg, 1 mmol) in methanol (10 mL) and stirred at 50 °C for 2.5 h under nitrogen atmosphere. Evaporation of the solvent on a rotary evaporator gave a powder, which was purihed on silica gel column chromatography using EtOAc and MeOH (15 5) as eluent to afford complex 1 as a green powder (70% yield). 

---