# The Attachment of Carbon Nanotubes to Atomic Force Microscopy Tips Using the Pick-Up Method
## 1 Introduction
One of the more recent commercially available options AFM scientists have access to is high-speed AFM or fast scanning AFM [18; 19; 44] which has the potential to observe chemical and biological processes in real-time. [PERSON] et al. [53] determined that the applied force the AFM tip experiences is proportional to the impact speed of the tip, which is also proportional to the probe tapping frequency. Fast scanning AFM probes have resonant frequencies in the MHz range which is up to 10 times larger than typical tapping mode probes. This means that AFM probes with higher resonant frequencies \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Manufacturer**} & **AFM Probe Type/Tip** & **Nominal Spring** & **Mode of Operation** & **Nominal Tip** & **Tip Features** \\  & **Composition** & **Constant (N/m)** & **Mode** & **Diameter (nm)** & **Tip Features** \\ \hline Mikromasch & HiResC/Silicon & 5 & Tapping & 2 & Small diameter \\ \hline Bruker & Scan Asyst air/Silicon & 0.4 & Peak-force tapping & 4 & Small diameter \\ \hline Bruker & \begin{tabular}{c} DC540/high \\ density carbon \\ \end{tabular} & 42 & Tapping & 40 & High aspect ratio \\ \hline Nanoworld & S8S-NCH/Silicon & 42 & Tapping & 4 & Small diameter \\ \hline Nanoworld & DT-NCH/Diamond & 80 & Tapping & 300 & Wear resistance \\ \hline Nanoworld & AR5-NCH/Silicon & 42 & Tapping & Less than 20 nm & High aspect ratio \\ \hline Budgetsensors & \
\begin{tabular}{c} SHR300/diamond \\ like carbon \\ \end{tabular} & 40 & Tapping & 2 nm &
\begin{tabular}{c} Small diameter/ \\ wear resistance \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Shows types of AFM probes currently available on the market that meet some of the requirements of CNT-AFM probes. will impact the sample surface with higher velocity and, therefore, increased force which can result in increased tip wear. [PERSON] et al. [44] showed that CNTs attached to the tips of probes specially designed for fast scanning are more resistant to wear than the silicon tips. Another area of AFM research that CNT-AFM probes have been used is conductive AFM. [PERSON] et al. [54] showed that CNT-AFM conductive probes can achieve high resolution conductivity images and are more durable than standard conductive AFM probes. The method employed by [PERSON] et al. [54] to create their conductive CNT-AFM probes used a FIB/SEM to attach the CNT to the AFM tip. [PERSON] et al. [55] also used an SEM to attach a SWCNT to an AFM tip which was welded to the tip by focussing the SEM beam onto the CNT/tip junction. This produced an amorphous carbon layer which pinned the CNT to the AFM tip surface. [PERSON] et al. [56] and [PERSON] et al. [57] also developed methods of producing conductive CNT-AFM probes by attaching multi-walled CNTs to metal coated AFM tips. [PERSON] et al. [56] used a technique based on dielectrophoresis while [PERSON] et al. [57] welded CNTs onto AFM tips by flowing DC current through the AFM tip and attached CNT. Attaching CNTs to AFM tips also means that the tip now essentially acts as an anchor point for the CNT. Therefore, blunt and used tips can be reused as CNT-AFM tips which is another advantage of these types of probes. However, the widespread use of CNT-AFM probes has diminished in the AFM community and is due to a number of factors including their tendency to only be applied to high spring constant tapping mode probes and the lack of methods that can attach CNTs to more than one AFM probe at a time. In this work we will demonstrate that one of the first methods developed [58] can be applied to contact mode cantilevers with low spring constant and can also produce two usable CNT-AFM probes in one process. One of the earliest methods developed to attach CNTs to AFM tips was developed by [PERSON] et al. [58] and involves the manual attachment of CNT to AFM tips through the imaging of CNT covered substrates. This is also known as the pick-up method and is one of the relatively simplest methods to attach CNTs to AFM tips.