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Layered nanostructures of copper metal and cuprous oxide are electrodeposited from alkaline solutions of Cu(II) lactate at room temperature. No subsequent heat treatment is necessary to effect crystallization. The electrode potential spontaneously oscillates during constant-current deposition. At a fixed current density the oscillation period decreases as either the pH or temperature is increased. The oscillations are periodic in stirred solution, but show period doubling and evidence of quasi-periodic or chaotic behavior in unstirred solution. The phase composition and resistivity of the films can be controlled by varying the applied current density. The resistivity of the films can be varied over ten orders of magnitude. Scanning electron microscopy shows that the films are layered.

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Quantum confinement of carriers in nanometer-scale materials leads to size-dependent optical and electrical properties that are intermediate between those of molecules and those of extended network solids. The quest in this area of research is to engineer a normally intrinsic property such as a semiconductor bandgap by simply changing the siLe of the material. Semiconductors in this size regime can also show enhanced carrier mobility, nonlinear optical properties, and quantized charge transport. Examples of quantum-confined materials include superlattices,i',2J quantum dots,["'1 and surface-confined systems such as quantum corralsi7] Work on chemically produced nanometer-scale materials has mostly focused on toxic, heavy-metal chalcogenides such as CdS and CdSe.[3,5,61 Since it is difficult to make actual devices out of individual quantum dots, these materials have not been technologically exploited. Here we show that composite films of cop-

Continuous films of silver(II) oxide (Ago) have been electrodeposited directly from aqueous solutions of 50 mM silver acetate/25 mM sodium acetate onto 430 stainless steel, polycrystalline platinum, and indium-tin oxide-coated glass. Current efficiencies for the electrodeposition process ranged from 62 to 95% and were a function of the applied current density. X-ray diffraction of the electrodeposited films reveals a [010] texture when the thickness is greater than 1 tim. Freshly ground films or powders exhibit only reflections consistent with the monoclinic Ago structure. Rietveld analysis confirms the ground films are single-phase Ago with a P 21/c space group. The films were imaged and film thickness was measured by atomic force microscopy. Thermogravimetric analysis shows that the films begin to decompose in air above 130°C, with an abrupt weight loss between 180 and 200°C. The total weight loss of 6.4 to 6.5% corresponds to thermal decomposition of Ago to Ag2O with loss of oxygen. A direct optical bandgap of 1.1 eV was measured. The black Ago films absorb strongly in the near infrared and throughout the visible region. The four-point resistivity of the Ago films was 12 1 11 cm.