Growth of Gold Dendritic Nanoforests on Titanium Nitride-coated Silicon Substrates

This protocol is a simple, quick, electrolyses deposition method for preparing gold dendritic nanoforests on a titanium nitride-coated silicon substrate. The main advantages of this technique are its simplicity and its speed. Gold dendritic nanoforests can induce plasmonic hotspots and enhance plasmonic photocatalytic reactions.

One can also use this procedure to prepare the dendritic nanoforests of alloy metals such as silver. Video demonstration makes it easier to emphasize essential details in the experiment. To begin the procedure, cut 10 two by two centimeter pieces of n-type silicon wafer.

Sonicate the silicon samples for five minutes each in acetone, isopropyl alcohol, and deionized water in sequence. Dry the samples for five minutes under a stream of nitrogen gas. Then, place the clean, dry silicon samples in a sample holder, and put the holder in a HiPIMS sample chamber.

Place a four inch diameter titanium target on a HiPIMS sputtering cathode, and pump down the HiPIMS chamber to eight times 10 to the negative six torrs. Deposit a 50 nanometer think layer of titanium on the silicon samples. Then, deposit titanium nitride to achieve a total titanium nitride thickness of about 300 nanometers.

When titanium nitride deposition is complete, combine 240 microliters of one molar chloroauric acid, eight milliliters of six to one buffered oxide etch, and 15.76 milliliters of deionized water in a polytetrafluoroethylene container. Immerse one substrate in the chloroauric acid solution for precisely three minutes, and then wash it with deionized water. Dry the sample under a stream of nitrogen gas and incubate it at 120 degrees Celsius for five minutes.

Repeat this process for each of the remaining titanium nitride coated substrates. When sample preparation is complete, characterize the samples with scanning electron microscopy and x-ray diffraction. Energy disperse of x-ray spectroscopy confirmed that gold structures had grown on titanium nitride coated silicon surfaces.

The titanium nitride film deposited on the silicon wafer was smooth and uniform. Within a minute of placing the sample in the growth solution, small gold nuclei appeared across the sample with a few larger nuclei that resembled sea urchins. Single tree-like structures were observed after three minutes of growth, with branching occurring after five minutes of growth.

After 10 minutes, the dendritic nanoforest covered the entire titanium nitrite surface. After 15 minutes, the dendritic nanoforest was dense and about five micrometers thick. The gold's dendritic nanoforest thickness was found to increase linearly with synthesis time.

The gold peaks in x-ray diffraction also increased over time while the titanium nitrite signals disappeared as the synthesis progressed. The most important things to remember when attempting this procedure is rate of composition and a PH of solution, also effect the method of deposition. It is possible to fabricate DNFs and other titanium nitrite coated substrates such as silica silicone, conventional glass, ITO glass, and the FDO glass for various applications.

One must be careful when handling the samples because it's easy to remove the golden DNFs from the titanium nitrite silicon substrates if the gold DNF there is sick enough. Remember to wear personal protective equipment when working with buffer oxide etch, which contains hydrogen fluoride.