Ion beam smoothing of CVD diamond thin films by etchback method

Taniguchi

2012

Conventional grinding and polishing mechanisms for fabricating ultra-sharp diamond knives often cause subsurface damage and micro-chipping at the cutting edge. Compared to mechanical methods, ion beam machining (IBM) is considered more suitable for nano-scale machining of diamond materials. But the problems associated with IBM are facet formation, ripples formation and high irradiation damage. In order to overcome all theses problems, we proposed a 500 eV O + /O + 2 ion beam machining for the fabrication of smooth and ultra-sharp diamond knives from mechanically coarse finished samples. In our method, the knives are irradiated at tilted condition to avoid facet formation at the cutting edge. To suppress ripples formation and obtain isotropic smoothening of the surface, the stage is simultaneously rotated around the axis of ion beam incidence. To reduce the irradiation damage, a low energy reactive ion species is used in this method. A simulation model is developed to predict the profile change of knives at different tilted conditions and then compared with experimentally obtained results. We achieved sharpening down of the apex angle from 90• to 68• and from 60• to 48• by 5 hrs of machining. We also successfully reduced down the diameter of tip from 5 µm to lower than 60 nm with an average cutting edge irregularity 20-40 nm.

Section: From 90mentioning

confidence: 99%

Section: From 90mentioning

confidence: 99%

Fabrication of Smooth and Ultra-Sharp Diamond Knives of Lower than 60 nm Tip Diameter by Low Energy Oxygen Ion Beam Machining

Taniguchi

2012

“…The value of the etching rate corresponding to the effective ion incidence angle, θ e can be obtained by using the experimental data of Kiyohara et al [28], and then the average etching rate V is derived for each cycle. Figure 3 shows the plots of the average etching rate against the vertical angle ϕ for the swing angle ±30…”

Section: Simulation Of the Profile Changes Of A Conical Type Diammentioning

confidence: 99%

Ion Beam Sharpening of a Diamond Knife without Facet and Ripple Formation by Swinging It

Fukuyama

Pahlovy

et al. 2012

Diamond is considered a promising candidate for the source material of various small scale mechanical tools and electro-mechanical and optical devices. Usually, the diamond tools are fabricated by conventional mechanical lapping method using fine diamond powder, and a lap-plate of soft material. But, these processes can cause microchipping in the cutting edges and hence they are not recommendable. FIB (focused ion beam) machining is found more effective for ultra-fine machining of diamond tools but in this process formation of ripples, high damage layer, slow processing and high running cost are some major drawbacks. In order to overcome these limitations, we applied low energy ion beam machining (IBM) using broad ion beam for the sharpening of diamond knife at normal ion incidence and fixed tilt angles. However, formation of facet and/or ripples becomes problematic in this case and the possible machining conditions such as ion beam energy and tilt angle of the tools are very limited. In order to broaden the possible machining conditions as well as get facet and ripple free sharp diamond knife, we proposed swinging of the sample during ion beam sputtering process. To understand the swinging effects on diamond knife, we at first conducted experiment on flat diamond substrates by sequential sharpening process with varying angle of ion incidence. We also developed a simulation method for predicting the profile changes of diamond tools due to IBM at different swing angles. From our experiment and simulation we found, we can get very smooth and sharp diamond knife at the swing angle of ±30• .

“…Conventionally, diamond nano-tip for AFM probes are fabricated using a combination of CVD-diamond film, standard lithography and dry etching process [9][10][11][12]. Among the dry etching processes, PE (plasma etching) [13], RIE (reactive ion etching) [14,15], IBM (ion beam machining) [16][17][18], RIBM (reactive ion beam machining) [18], IBAE (ion beam assisted etching) [19], RIBM (reactive ion beam machining) and FIB (focused ion beam) machining are being widely used [20,21] for ultra-fine machining of diamond tools. RIE, which is commonly used for surface micromachining of CVD diamond MEMS, cannot be applied for the forming and sharpening of diamond probes used in AFM because in this method the incident angle of the ions cannot be changed as required, hence it becomes difficult to control the shape of the diamond tip.…”

Section: Introductionmentioning

confidence: 99%

Low Energy Oxygen Ion Beam Machining of Ultra Smooth and Sharp AFM Nano-Tips from Single Crystal Diamond Rods

Miyamoto

Taniguchi

2012

Diamond made AFM probe exhibits a long life time as diamond has ultrahigh hardness, ultra high tensile strength and high wear resistance. For the ultra fine machining of diamond tip, focused ion beam (FIB) machining is being widely used but the process is very slow due to one by one processing and ripples are formed on the processed surface. Moreover, the irradiation damage and machining cost are significantly high. Compared to FIB machining, low energy broad ion beam machining (BIBM) is better suitable for the mass fabrication of AFM tips. In this paper, we presented a two stage BIBM process using 1-3 keV O + /O + 2 ion beam for the mass fabrication of ultra smooth and sharp AFM nano-tips from single crystal diamond rods. In order to suppress the ripple formation on the processed diamond tip, the sample was rotated during machining process. In our proposed method, around 100 ultra smooth and sharp AFM nano tips with the apex angle of 50 • and an average tip diameter of 22 nm can be simultaneously fabricated in just 1.5 hour. Moreover, the irradiation damage of the processed tip is also very low due to low energy ion beam machining and chemical etching of the amorphous carbon by the oxygen ions. A simulation model is developed to predict the profile change of diamond tip by low energy oxygen ion beam machining. At last, the mechanisms of fine sharpening and ultra smoothening of the diamond tips are discussed with the help of Witcomb formula and Bradley-Harper (BH) model.