Methods

Micro-contactprinting

Monolayer

UV mask

Micro-lithography

Limited by wavelength

X ~ m

~ 10nm

Nano-writing

Phase separated Langmuir-Blodgett Films

Oriented block co-polymers

Intermolecular interaction

X~ nm

Nanoisland

matrix

Chemical Functionalities Differing in size and type

Examples: CH3-, NH2-, CF3-, COOH-, halide, ethylene oxide

Island Surfaces are Formed By Using SAMs with Two Different Functional Groups

Substrate

Terminal FunctionalityAnchoring Functional-

ity

Surfactant type B

Surfactant typeA

Temp : 220C

OTS

Dehydrated Substrate

In 1.1 mM APhMS 60 sec

rinse in toluene

In 1.1 mM OTS soln60 min

CHCl3 rinse15 min 8 Å

Recessed Islands of APhMSIn OTS Background by Backfilling

0 5 P-Aminophenyltrimethoxy silane

m

Silicon waferOHOH OHOH OHOH OHOH

OTS

Ht difference :15 Å

Temp : 220C

Dehydrated Substrate

In 1.1 mM APhMS 60 sec

rinse in toluene

In 1.1 mM OTS soln60 min

CHCl3 rinse15 min 0 5

Recessed Islands of APhMSIn OTS Background by Backfilling

octadecyltrichlorosilanem

Silicon wafer

Method B: Co-Adsorption

Mixed monolayer of OTS and APS(NH2C3H6SiCl3)

Silicon wafer

CH3

23Å

6.5Å

30nmamine

APhMSOTS

octadecyltrichlorosilanes (OTS) P-aminophenyltrimethoxysilanes (APhMS)

Island Formation of Co-Adsorbed Self-assembling

SurfactantsAPhMS islands in OTS Matrix

0

5

10

15

20

25

30

10 13 15 18 22 25 28 31 34 37 40 43 50

Diameter (nm)

35 islands/µm2, average diameter: 28 nm,distribution width: 10 nm

3:1 OTS:APhMS; Chloroform

2mM total concentration of silane

Effect of Composition2 mM CHCl3 solution, deposition time; 2 hrs

OTS/APMS=1:3 OTS Pillars

OTS/APMS=3:1 APhMS islands

OTS/APMS=1:1 OTS Pillars

Contact Angles: 80 Contact Angles: 41

Solvent Effect2 mM solution (OTS/APhMS=1:1), deposition time: 2 hrs,

CHCl3Toluene

CCl4 THF

Contact Angles: 103 Contact Angles: 98

Effect of Solvent on Composition

Monolayer Composition in Mixed Adsorption is a balance between

• relative affinity of surfactants to the depositing solvent

• interfacial energy between the film formed and the depositing solution

Sequential Adsorption for Mixed Monolayers

Partial OTS monolayers with desired islands Low density surrounding OTS islands at100C.

SOLVENT

SUBSTRATE

OTS SOLUTION

SUBSTRATE

SECOND SILANE SOLUTION

Rinse

Fill surrounding with second silane

Temperature Effect

100C

~220CReduced Secondary growth at low temperatures

Control of Morphology and Chemical Functionality at

Nanometer Scale

Mixed monolayer of OTS and BrUTS(BrC11H22SiCl3)

Silicon wafer

CH3

23Å

15Å

30nm to 10 µm Br

10 2

Height HeightFriction Friction

Control of Morphology at Angstrom Scale

Mixed monolayer of OTS and DTS(C10H21SiCl3)

Silicon wafer

CH3

23Å

14Å

30nm to 10 µm

10

Height Friction

Nano-dots

5

Low OTS concentration & low deposition time

pH 8. . .

Imaging at loads of ~ 1.5 GPa (70 nN). . .3 scans

unworn unwornworn. . . leads to rapid pit formation and facile dissolution

pH 5. . . Imaging at loads of ~ 0.7 GPa (58 nN). . .10 scans

. . . friction appears to be decreasing. . . surface roughens by ~ 0.5 Å

. . . charging followed by surface atom abstraction is observed

nativeIn wear

pH 5. . . Imaging at loads of ~ 1.6 GPa (96 nN). . . 10 scans

pH 3. . . Imaging at loads of ~ 0.7 GPa (56 nN). . .83 scans!

. . . no wear to be found, even with increased loads!

. . . no charging due to low [OH-].

Studies of Lubricant Films: Functionalization of AFM tip and Particle Surface

CH3(CH2)17-Si(OCH2CH3)3

(OTE)

Functionalization with organosilanes:

Si(100)

Contact angle with water on OTE modified particle films

- Forms self-assembled monolayers on silica.- Have been used in MEMS devices.

AFM Tip

Thiols on Au…

Salmeron and Liu

Nanopatterning of Surfaces

AFM STM

Liu et al, Acc. Chem. Res. 33 (2000) 457.

C18S/Au

C18S implanted in a C10S/Au

Mirkin dip-pen lithography

Allows fab in air!

Amro et al, Langmuir 16 (2000) 3006.