VistaScope: Photo-Induced Force Microscope (PiFMP)

The ground-breaking Photo-induced Force Microscopy (PiFM) mode is integrated into all VistaScope models. The PiFM mode measures the polarizability of the sample with high sensitivity and nanometer spatial resolution.

The VistaScope is a high-resolution and high-performance AFM with a state-of-the-art controller and exceptional top optics for an overhead view of the tip and sample. At a variety of optical resonances (electron, plasmon, phonon), PiFM signal is significantly enhanced and creates spectral images with unparalleled SNR.

Optical Access 360°

The VistaScope platform enables optical access from the side, top, and inverted geometry. The infrastructure that enables these pathways was developed to suit users looking for a ‘black box’ solution, as well as users who would like to additionally customize their optical pathways.

Standard cage-mounting provides the users with the flexibility to hack into their system and design a specific experiment. However, Molecular Vista will install the VistaScope with optics aligned, ready for near-field signal from the first day. This configuration can be maintained with minimal to zero effort for the user.

Technical Info

AFM-BD Head

The AFM-BD (Beam Deflection) Head is the standard AFM head with the VistaScope package. It has an ultralow noise sensor (< 25 fm/Hz½) and an in-built parabolic mirror for efficient side illumination/collection for PiFM and scattering SNOM on opaque samples. It is highlighted by the following features:

  • Easy-to-use open liquid cell
  • Fabricated out of invar for thermal stability
  • Photodiode bandwidth: DC to 6 MHz
  • High-speed Z-piezo for dual-z feedback control
  • Adaptable focus size for ultra-small cantilevers
  • Manual offset XY stage for coarse tip-laser (external) alignment
  • Selection of 650 nm or 980 nm laser for beam deflection sensor
  • Ultra low profile (11 mm thick) for use of high NA (0.6 NA) top objective lens
  • Rigid yet easy-to-change cantilever holder
  • Integrated parabolic mirror with 3D piezo-motor alignment stages

Frame/Stage/Scanner

The frame is built to be sturdy and stable; to realize maximum stability, its footprint matches an active vibration isolation table (optional)  The standard noise level is below 0.05 nm RMS with a functional high NA inverted optical microscopy unit. The basic setup features include:

  • Motorized sample approach
  • 40 x 40 x 10 µm3 flexure scanner
  • Compatible with top/side/inverted optics
  • Motorized XY sample stage (+/- 3 mm)
  • Scanner fabricated out of invar for thermal stability
  • Both motorized stage and scanner with hole for inverted objective lens
  • Optional active vibration isolation table

Top Optics

The top optics is designed to provide a clear view of the cantilever and sample surface with zoom capability. The flexible design is based on a standard cage system so that the optical pathway and its functionality can be easily adapted and augmented.

The basic setup features the following:

  • 20X, 0.6 NA LWD Lens
  • Motorized focus
  • LED lighting
  • CCD viewing

The figures below illustrate two of several configurations that can be housed with the top optics due to employment of the cage system.

Standard configuration of the top down optics where it is primarily used as a zoom-capable cantilever/sample monitor.

An alternate configuration where in addition to its function as cantilever/sample monitor, a fiber-coupled laser can be collimated and focused onto the tip/sample region.

Examples of the CCD views are illustrated below. The repeating features illustrated in the CCD view have a pitch of 10 µm.

100% CCD View

200% CCD View. The zoom extends to 600%.

Side Optics

The two side optical configurations are totally compatible with both the top and inverted optics. One is based on the integrated parabolic mirror, and the other is based on a side objective lens.

Parabolic Mirror:

  • PiFM compatible
  • User exchangeable dichroic, emission filters, and excitation filters
  • Raman, photoluminescence, and fluorescence collection
  • Scattering SNOM interferometric detection
  • Fiber or freespace optical excitation and detection

Side Objective Lens:

  • PiFM compatible
  • Objective lens: 0.42 NA LWD
  • User exchangeable dichroic, emission filters, and excitation filters
  • 100 mm tube lens (other options available)
  • Raman, photoluminescence, and fluorescence collection
  • Fiber or freespace optical excitation and detection
  • Camera view of sample tip area

Inverted Optics Module

Completely compatible with the top and side optics, the inverted optics allows the application of the highest NA objective lenses for transparent substrates.

  • 150 mm tube lens
  • High NA oil coupled objectives and reflective objectives (for mid-IR)
  • PiFM compatible
  • User exchangeable dichroic, emission filters, and excitation filters
  • Supports objectives with parfocal length of 45 mm by design, but other lengths can be considered
  • Raman, photoluminescence, and fluorescence collection
  • Camera view of sample tip area
  • Fiber or freespace optical excitation and detection

A variety of expansion ports are provided in the frame for integrating extra light sources and detectors for varied imaging modes.

Controller

The controller is future-proof with advanced capabilities not available with any other AFM controllers. This controller comes with two inputs with 500 million sampling per second (MSPS) capability together with four two-phase lock-in amplifiers.

In addition to the functions available in other high-end AFM controllers, some of the unique features include:

  • Dual-z feedback capability enables control of two z-piezo scanners, one with high bandwidth (on the tip) and the other with a modest bandwidth (on the sample) to obtain large range as well as high-speed and very accurate z movements
  • Concurrent imaging of multiple modalities at many frequencies (for example, AFM topography at dither frequency, scattering SKPM signal at the second mechanical resonance of the cantilever and SNOM signal at the third harmonic of the dither frequency all at the same time)
  • Patented lock-in detection for background suppression of scattering SNOM
  • Side-band force gradient measurements for different types of tip-sample interaction forces
  • Many feedback modes: contact and dynamic mode AFM, STM, and PLL (for high Q sensors such as tuning fork)
  • Advanced two-channel modulation output from the integrated lock-in amplifiers for current modulation of Bragg cells, diode lasers, or other external devices for sensitive lock-in measurements simultaneous with AFM topography measurements
  • Support for single-photon counters and a modern Raman spectrometer for confocal and tip-improved spectral Raman and fluorescence imaging
  • Flexible spectroscopy operation that allows monitoring of any signal as a function of tip-sample spacing

Software

VistaScan

The VistaScan offers a full and easy-to-use user interface to fully access and utilize VistaScope’s advanced controller and its large number of hardware components.

  • Q-control
  • Automatic detection of 1st and 2nd resonances for Multi-Modal Imaging
  • Powerful spectroscopy to obtain multiple channels vs gap spacing
  • Lock-in Amplifier UI to obtain multiple force and force gradient signals
  • Dual-Z Feedback for use of both standard and fast Z-Piezo elements
  • Customizable signals to modulate external lasers or Bragg cells
  • UI for Scattering SNOM with Background Suppression
  • UI for Image Force and Stimulated Raman Force Microscopy
  • UI for Scanning Kelvin Probe Microscopy (Force or Force Gradient Techniques)

SurfaceWorks

The SurfaceWorks is a powerful and smart image process and analysis package. All of the processes and analysis are employed as functions to images while keeping the raw data files intact.

  • Multi-channel comparison
  • Multi-image comparison
  • Flexible image management
  • Shape-based and histogram-based masks
  • Preview feature for most functions
  • All functions (Flattening, Line & Region Analysis, 3D Render Properties, Palettes, etc.) associated and transferable with raw image files
  • Batch processing by copying and pasting functions

Screen capture of Line Analysis function. The analysis is saved with the raw data file so that it is displayed when the image file is loaded next time.

Screen capture of Palette function. The preview of the image with various palettes is shown on the left panel. Any of the pre-defined palettes can be edited and saved as a new palette.

Specifications

Beam Deflection AFM Head (AFM-BD)

  • Body profile: 11 mm thick
  • Body material: Invar for excellent thermal stability
  • AC detector noise: <25 fm/root Hz above 100 KHz
  • BB laser source: 650 nm or 904 nm
  • Detector bandwidth: 6 MHz
  • Fast-Z module: 1 µm z-piezo as the fast-Z element of dual-Z feedback system
  • Manual translation stage: 3 mm movement in XY for coarse tip alignment to external laser (for tip-enhanced spectroscopy)
  • Focus size: Adjustable to accommodate various cantilevers including the ultra-small ones for high speed imaging
  • Operational mode: ambient or open liquid cell
  • Optional component: Integrated parabolic mirror with 3D piezo-motor stage for reflection mode PiFM and s-SNOM

Forward Facing Tuning Fork AFM Head (AFM-FFTF)

  • TF operation: Tapping-mode
  • Body material: Invar for superior thermal stability
  • Manual translation stage: 3 mm movement in XY for coarse tip alignment to external laser (for tip-enhanced spectroscopy)
  • Integrated tip scanner: XY flexure stage scanner for the TF with 12 µm x 12 µm range
  • Fast-Z module: 1 µm z-piezo as the fast-Z element of Dual-Z feedback system

Main Body Frame

A custom designed inverted optical microscope with rigid and compact frame acts as the platform for very high resolution microscopy.

  • Inverted objective lens: 100X, 1.4NA Oil; 60X, 0.9A air
  • Top objective lens: 20X, 0.6NA
  • Top objective lens focus: Motorized
  • Tip alignment mechanism: Piezo-driven XYZ stage (12 µm for XY and 100 µm for Z) for the inverted objective lens for precise alignment of the focus spot onto the tip
  • Sample stage: Motorized precision stage with 6 mm x 6 mm travel range
  • Maximum sample size: 25 mm x 25 mm x 5 mm
  • Illumination: Software-controlled LED
  • CCD camera: Concurrent top and inverted views with 1280 x 1024 pixels each; digital zoom, pan, and capture
  • Tip-sample approach: Automated engagement via three stepper motors
  • Sample scanner: XYZ flexure stage scanner with 30 µm x 30 µm x 7 µm scanning range (closed loop); 40 µm x 40 µm x 10 µm for open loop; Z sample scanner serves as the slow Z component of Dual-Z feedback system; other ranges available upon request
  • System noise: <50 pm RMS (dependent on environment)
  • Scanner sensor noise: 1 nm for XY with 40 kHz bandwidth 0.5 nm for Z with 40 kHz bandwidth
  • Optical configuration: Based on standard 1" cage system for expansion flexibility
  • Side optics module: Available as option for PiFM, scattering SNOM, and TERS on opaque samples
  • Scanner material: Invar for excellent thermal stability
  • Optional components: Active vibration isolation table for low noise performance

High-Speed Electronics

The FPGA-based control electronics has a section exclusively for high-speed scanning probe microscopy.

  • Sampling rate: >500 MHz for channels A and B; Channel A dedicated for photodiode detection for high-speed AFM
  • Maximum feedback throughput: 1 Mps with Dual-Z feedback
  • High-speed sine wave generator: Two channels with 160 MHz sampling rates; one reserved for scan generator for high-speed AFM
  • Lockin amplifiers: Four independent two-phase Lockin amplifiers (LIA0 to LIA3)
  • LIA operation frequency: Up to 10 MHz
  • High-speed feedback mode: Dual-Z feedback where the sample scanner tracks the slow varying topography and the Fast-Z Module in the AFM head tracks the fast varying topography

Standard-Speed Electronics

  • ADCs: 8X 24-bit, 156 kHz; 4X 24-bit, 156 kHz
  • DACs: 8X 24-bit 156 kHz; 2X 24-bit 156 kHz; 1X 20-bit, 156 kHz
  • Stepper motor control: Three channels
  • DC motor control: Three channels with encoders and Schmitt-Trigger for improved signal quality
  • HV-Amplifiers: 10 channels
  • Noise Floor for Scan HV-Amplifiers: 140 uVrms for 150 V full range

PiFM and Optics Electronics

Electronics for PiFM includes:

  • TTL Signal Generator: Two flexible TTL signal generators (with 160 MHz sampling rate) with modifiable duty cycle and DC offset for direct current modulation of laser diodes or for input to Bragg cells
  • Digital Counter Input: Input for APD and PMT for low-lighting imaging
  • Flexible Lockin Referencing: The LIAs can be phase locked to any other LIA or at any calculated frequencies from the other LIAs

Computer

The computer is fitted onto a 19" rack. Minimum configuration includes 3.4 GHz Quad Core, 4 GB RAM, 2000 GB HD and 256 GB SSD combination, 8X USB ports, 26" or larger monitor, and Windows 7 Professional.

VistaScan Image Acquisition Software

Supported modes/features include:

  • Contact and AC AFM
  • Q-control
  • STM and PLL feedback (for high Q sensors such as tuning-fork)
  • Ultrafast Dual-Z feedback
  • Sideband force gradient imaging (for KPFM via electric force gradient detection)
  • Bi-modal force gradient imaging for non-linear and linear PiFM
  • Simultaneous acquisition of 26 channels in Dual-Z configuration and 40 channels in Slow-Z configuration
  • Simultaneous acquisition of four channels for each spectroscopy mode which may include
    • vs bias with and without feedback
    • vs gap distance
    • step response to voltage response with and without feedback

SurfaceWorks Image Analysis Software

The SurfaceWorks Image Analysis Software is a powerful and intuitive software. The features include:

  • Functions and analysis (FFT filtering, flattening, line & region analysis, palettes, 3D rendering, etc) applied to an image saved as a file property along with the raw data file
  • Shape and histogram-based masks
  • Copy/Paste file property to apply same analysis and functions to other image file(s)
  • Preview feature for a majority of functions

Acoustic Enclosure

An optional acoustic enclosure (30 W x 30 D x 27 H in3) can be ordered with or without temperature control; offered along with ports for cables and optical access

Other Equipment