Soft ionization device with characterization systems and methods of manufacture

• US 6,828,552 B2
• Filed: 06/02/2003
• Issued: 12/07/2004
• Est. Priority Date: 06/25/2001
• Status: Expired due to Fees

• Current Assignee: Ionfinity LLC (VIASPACE, Inc.)
• Original Assignee: Ionfinity LLC (VIASPACE, Inc.)
• Inventors: Hartley, Frank T.
• Primary Examiner(s): BERMAN, JACK I
• Application Number:
  US10/452,343
• Publication Number:
  US 20030201389A1
• Time in Patent Office: 554 Days
• Field of Search: 250/287, 250/423.F, 250/423.R, 313/230
• US Class Current: 250/287
• CPC Class Codes: F03H 1/00 Using plasma to produce a reactive propulsive thrust generating plasma H05H1/00 ion sources per se H01J27/02, ion sources for plasma processing or ion beams H01J37/08
• CPC Class Codes: H01J 27/26 using surface ionisation, e.g. field effect ion sources, thermionic ion sources H01J27/20, H01J27/24 take precedence
• CPC Class Codes: H01J 49/168 field ionisation, e.g. corona discharge atmospheric pressure corona discharge per se H01T19/00
• CPC Class Codes: Y10S 977/89 Deposition of materials, e.g. coating, cvd, or ald

Abstract

Various configurations of characterization systems such as ion mobility spectrometers and mass spectrometers are disclosed that are coupled to an ionization device. The ionization device is formed of a membrane that houses electrodes therein that are located closer to one another than the mean free path of the gas being ionized. Small voltages across the electrodes generate large electric fields which act to ionize substantially all molecules passing therethrough without fracture. Methods to manufacture the mass spectrometer and ion mobility spectrometer systems are also described.

Claims

1. A system for ionizing a sample of molecules, comprising:

an ionizing device, comprising a substrate having at least one opening, a first conductive electrode extending on a first surface of the substrate and a second conductive electrode extending on a second surface of the substrate, and a separator insulating element, having a thickness less than a mean free path of a molecule being ionized, separating said first and second conductive electrodes at said at least one opening, said first and second conductive electrodes being separated by a width of said separator insulating element; and

a characterization unit coupled to said ionizing device, for receiving and characterizing ionized molecules from said ionizing device.

2. A system as in claim 1, wherein said first and second conductive electrodes are separated by less than 1 micron at said at least one opening.

3. A system as in claim 1, wherein said first and second conductive electrodes are separated by less than 300 nm at said at least one opening.

4. A system as in claim 1, wherein said first and second conductive electrodes are separated by less than 200 nm at said at least one opening.

5. A system as in claim 1 wherein said first and second conductive electrodes are separated by approximately 50 nm at said at least one opening.

6. A system as in claim 1 wherein said at least one opening tapers inwardly from the first surface of the substrate to the second surface of the substrate.

7. A system as in claim 1 wherein said at least one opening has a diameter approximately in the range of 2-3 microns.

8. A system as in claim 1, wherein said first and second electrodes are formed of one of gold, chrome or titanium.

9. A system as in claim 1, wherein said separator insulating element is a dielectric.

10. A system as in claim 9, wherein said separator insulating element is formed of silicon nitride or alumina.

11. A system as in claim 1, further comprising a lateral accelerator disposed between said ionizing device and said characterization unit for accelerating ions from said ionizing device to said characterization unit.

12. A system as in claim 11, wherein the accelerated ions are induced to traverse through said characterization unit without a pump.

13. A system as in claim 1, wherein said characterization unit is a Faraday cup electrometer ion detector.

14. A system as in claim 1, wherein said characterization unit is an ion mobility spectrometer.

15. A system as in claim 14, wherein said ion mobility spectrometer operates at substantially ambient pressure.

16. A system as in claim 15, further comprising a gas feed system to carry ionized gas molecules through said ion mobility spectrometer away from said ionizing device.

17. A system as in claim 16, wherein said gas feed system is an upstream gas carrier supply and a Venturi sampler.

18. A system as in claim 16, wherein said gas feed system is a downstream peristaltic pump.

19. A system as in claim 14, wherein said ion mobility spectrometer comprises a pair of filter electrodes which are configured to generate electric fields that control dispersal of ions received by said ion mobility spectrometer.

20. A system as in claim 19, wherein said pair of filter electrodes are configured to generate an electric field by applying a short high-voltage and a long lower voltage to said plurality of filter electrodes.

21. A system as in claim 19, wherein said filter electrodes generate an output having a zero tune averaged field.

22. A system as in claim 19, wherein said pair of filter electrodes are configured to generate an alternating electric field and a sweeping DC field for the transverse dispersal of ions received by said ion mobility spectrometer.

23. A system as in claim 19, wherein said pair of filter electrodes are configured to sequentially sweep the spectrum of ion species to detector electrodes.

24. A system as in claim 14, wherein said ion mobility spectrometer comprises a plurality of filter electrodes which are driven with electric fields that control ion dispersal.

25. A system as in claim 24, wherein said plurality of filter electrodes are configured to generate an alternating electric field and an opposing DC electric field for the transverse dispersal of ions received by said ion mobility spectrometer.

26. A system as in claim 24, wherein said plurality of filter electrodes are configured to generate an electric field by applying a short high-voltage and a long lower voltage to said plurality of filter electrodes.

27. A system as in claim 26, wherein said plurality of filter electrodes generates an output having a zero time averaged field.

28. A system as in claim 19, wherein said ion mobility spectrometer comprises at least two detector electrodes configured to detect impingement of ions at a specified location.

29. A system as in claim 28, wherein the molecules are continuously ionized and concurrently dispersed as ions to specific locations on said detector electrodes.

30. A system as in claim 28, wherein said detector electrodes are configured to directly measure ion current to determine the number of ions of a particular species contact said detector electrodes.

31. A system, as in claim 1, wherein said ionizing device ionizes all molecules passing therethrough without fracture such that a percentage of a particular species of ionized molecules is proportional to a vapor concentration of the particular species of ionized molecules.

32. A system as in claim 1, wherein electrons generated by said ionizing device move in a direction opposite to the generated ions and ionize further gas.

33. A system as in claim 1, wherein said characterization unit is a mass spectrometer.

34. A system as in claim 33, wherein said mass spectrometer system includes a solid-state electrode sensor array that detects ions.

35. A system as in claim 33, wherein said mass spectrometer system includes a time of flight system.

36. A system as in claim 33, wherein said mass spectrometer system comprises an array of pixellated electrodes.

37. A system as in claim 36, wherein said array of pixellated electrodes comprises an electrode sensor of 1024 by 1024 pixels.

38. A system as in claim 36, wherein said array of pixellated electrodes has a detection sensitivity of approximately 10⁻

17 amps.

39. A system as in claim 33, wherein said mass spectrometer operates at a pressure of approximately 5 to 7 Torr.

40. A system as in claim 1, wherein said ionization device is configured to receive an exhaled breath from a patient and said characterization unit is configured to characterize the exhaled breath.

41. A system as in claim 40, wherein said characterization unit is configured to quantitate carbon monoxide within the exhaled breath.

42. A system as in claim 1, wherein said characterization unit is configured to analyze a sample passing therethrough for an application chosen from the group comprising:

environmental monitoring, personal monitoring, water quality monitoring, automobile MAP control, detecting explosives, detecting chemical and biological agents, olfactory simulation.

43. A system for ionizing and detecting a sample of gas, comprising:

an ionizing device, comprising a substrate having at least one opening, a first conductive electrode extending on a first surface of the substrate and a second conductive electrode extending on a second surface of the substrate, said substrate having a thickness less than a mean free path of a gas molecule being ionized, separating said first and second conductive electrodes at said at least one opening, said first and second conductive electrodes being separated by a width of said substrate, wherein said ionizing device is configured to receive a continuous flow of sample gas; and

a characterization unit coupled to said ionizing device, for receiving ionized molecules from said ionizing device.

44. A system for ionizing a sample of molecules, comprising:

an ionizing membrane having;

a thick supporting portion with a first surface and with openings formed in the thick supporting portion;

an insulating element with first and second surfaces, wherein the insulating element is coated on the first surface of the thick supporting portion and terminates at a first end within the openings to form holes;

a first electrodes coated on the first surface of the insulating element that approximately terminates at the first end of said insulating element;

a second electrode coated on the second surface of the insulating element that approximately terminates at the first end of said insulating element; and

wherein a distance between the first and second metal electrodes within the holes is less than the mean free path of a material being ionized; and

a characterization unit coupled to said ionizing membrane configured to receive ions from said ionizing membrane.

45. A method comprising the steps of:

forming a layer of thin dielectric material on a substrate that has a first specified thickness of a sufficient thickness to maintain structural integrity;

forming a first electrode on the first surface of said thin dielectric material, said first electrode being formed of a metal material;

back etching at least one hole in said substrate;

forming a second electrode an a second surface of the substrate including the at least one back etching holes, such that at least a portion of the second electrode is on a second surface of the thin dielectric material; and

forming holes in the second electrode, thin dielectric material and the first electrode, which holes have side surfaces where the first and second electrodes are separated by a width of the thin dielectric material;

applying a voltage across said first and second electrodes to generate a field to ionize molecules passing through the at least one hole; and

providing a characterization unit coupled to the at least one hole for receiving ions generated by the ionizing device.

46. A method as in claim 45, wherein said thin dielectric material has a thickness which is less than the mean free path of the gas intended to be ionized by the ionization membrane.

47. A method as in claim 45, wherein said forming electrodes comprises depositing gold, chrome, or titanium.

48. A method as in claim 45, wherein said forming a thin dielectric comprises depositing silicon nitride or alumina.

49. A method as in claim 45, wherein said thin dielectric has a thickness less than 500 nm.

50. A method as in claim 45, wherein said thin dielectric has a thickness less than 300 nm.

51. A method as in claim 50, further comprising the step of applying a voltage less than 15 volts between said first and second electrodes to form a field between said first and second electrodes in the range of megavolts per meter.

52. A method as in claim 45, wherein said thin dielectric has a thickness of approximately 50 nm.

53. A method as in claim 45, wherein said forming holes in the second electrode comprises ion-beam milling.

54. A method as in claim 45, wherein said forming a thin dielectric comprises silicon nitride or alumina.

55. A method as in claim 45, wherein said back etching at least one hole in said substrata forms at least one hole tapered inwardly.

56. A method as in claim 45, wherein the holes formed by said forming holes in the second electrode, thin dielectric material and the first electrode are approximately 2-3 microns in diameter.

57. A method comprising the steps of:

forming a layer of thin dielectric material on a substrate that has a first specified thickness of a sufficient thickness to maintain structural integrity;

forming a first electrode on the first surface of said thin dielectric material, said first electrode being formed of a metal material;

forming at least one hole in said substrate;

forming a second electrode on a second surface of the substrate including the at least one hole in said substrate, such that at least a portion of the second electrode is on a second surface of the thin dielectric material;

forming at least one hole in the second electrode, thin dielectric material and the first electrode, which at least one hole has side surfaces where the first and second electrodes are separated by a width of the thin dielectric material;

applying a voltage across said first and second electrodes to generate a field to ionize molecules passing through the at least one hole; and

providing a characterization unit coupled to the at least one hole for receiving ions generated by the ionizing device.

58. A method as in claim 57 wherein said forming at least one hole in said substrate comprises ion-beam milling.

59. A method as in claim 57 wherein said forming at least one hole in the second electrode, thin dielectric material and the first electrode comprises ion-beam milling.

60. A method as in claim 57, wherein said thin dielectric material has a thickness which is less than the mean free path of the gas intended to be ionized by the ionizing source.

61. A method as in claim 57, wherein said forming electrodes comprises depositing gold, chrome or titanium.

62. A method as in claim 57, wherein said thin dielectric comprises silicon nitride or alumina.

63. A method as in claim 57, wherein said thin dielectric has a thickness less than 500 nm.

64. A method as in claim 57, wherein said thin dielectric has a thickness less than 300 nm.

65. A method as in claim 57, wherein said thin dielectric has a thickness loss than 200 nm.

66. A method as in claim 57, wherein said thin dielectric has a thickness of approximately 50 nm.

67. A method as in claim 57, further comprising applying a voltage less than 15 volts between said first and second electrodes to form a field between said first and second electrodes in the range of megavolts per meter.

68. A method as in claim 57, wherein said forming at least one hole in said substrate forms at least one hole tapered inwardly.

69. A system, comprising:

an ionizing device, comprising a support member having at least one opening, a first conductive electrode extending on a first surface of the support member and a second conductive electrode extending on a second surface of the support member, and separator means for separating said first and second conductive electrodes by a width of said separator means, wherein said separator means has a thickness less than the mean free path of the material being ionized; and

characterization means coupled to said ionizing device for detecting ions generated by said ionizing device.

70. A system as in claim 69, wherein said separator means separates said first and second conductive electrodes by less than 1 micron at said at least one opening.

71. A system as in claim 69, wherein said separator means separates said first and second conductive electrodes by less than 300 nm at said at least one opening.

72. A system as in claim 69, wherein said separator means separates said first and second conductive electrodes by less than 200 nm at said at least one opening.

73. A system as in claim 69, wherein said separator means separates said first and second conductive electrodes by less than 50 nm at said at least one opening.

74. A system as in claim 69 wherein said at least one opening tapers inwardly from the first surface of the support member to the second surface of the support member.

75. A system as in claim 69 wherein said at least one opening has a diameter approximately in the range of 2-3 microns.

76. A system as in claim 69, wherein said separator means comprises a dielectric.

77. A system as in claim 69, wherein said separator means is formed of silicon nitride or alumina.

78. A system as in claim 69, wherein said first and second electrodes are formed of one of gold, chrome or titanium.

79. A system as in claim 69, wherein said characterization means comprises an element which receives ions from said ionizing device.

80. A system as in claim 69, wherein said characterization means is a Faraday cup electrometer ion detector.

81. A system as in claim 69, wherein said characterization means is an ion mobility spectrometer.

82. A system as in claim 81, wherein said ion mobility spectrometer operates at substantially ambient pressure.

83. A system as in claim 81, further comprising a gas feed system to carry ionized gas molecules through said ion mobility spectrometer away from said ionizing device.

84. A system as in claim 83, wherein said gas feed system is an upstream gas carrier supply and a Venturi sampler.

85. A system as in claim 83, wherein said gas feed system is a downstream peristaltic pump.

86. A system as in claim 81, wherein said ion mobility spectrometer comprises at least two filter electrodes which are driven with electric fields that control ion dispersal.

87. A system as in claim 86, wherein said at least two filter electrodes are configured to generate an electric field by applying a short high-voltage and a long lower voltage to said plurality of filter electrodes.

88. A system as in claim 87, wherein said at least two filter electrodes produces an output having a zero time averaged field.

89. A system as in claim 86, wherein said at least two filter electrodes are configured to generate alternating electric fields and an opposing DC electric field for the transverse dispersal of ions received by said ion mobility spectrometer.

90. A system as in claim 81, wherein said ion mobility spectrometer comprises at least two detector electrodes configured to detect impingement of ions at a specified location.

91. A system as in claim 69, wherein electrons generated by said ionizing device move in a direction opposite to the generated ions and act to further ionize molecules.

92. A system as in claim 69, wherein said characterization means is a mass spectrometer.

93. A system as in claim 92, wherein said mass spectrometer system includes a solid-state electrode sensor array that detects ions.

94. A system as in claim 92, wherein said mass spectrometer system includes a time of flight system.

95. A system for ionizing and characterizing a sample of gas, comprising:

an ionizing device, comprising a substrate having at least one opening, a first conductive electrode extending on a first surface of the substrate and a second conductive electrode extending on a second surface of the substrate, said substrate having a thickness less than a mean free path of a gas molecule being ionized, separating said first and second conductive electrodes at said at least one opening, said first and second conductive electrodes being separated by a width of said substrate;

a characterization unit coupled to said ionizing device, for receiving ionized molecules from said ionizing device; and

wherein said characterization unit and said ionizing device may operate at substantially ambient pressure.

96. A mass spectrometer system comprising an ionization source and a plurality of detector electrodes, wherein said ionizing source comprises two electrodes having a spacing less than a mean free path of a molecule being ionized which generate electric fields that ionizes substantially all molecules without fragmentation and said detector electrodes characterize the ionized molecules.

97. A system for ionizing a sample of gas comprising:

an ionizing device, comprising a substrate having at least one opening, a first conductive electrode extending on a first surface of the substrate and a second conductive electrode extending on a second surface of the substrate, said first and second conductive electrodes being separated at said at least one opening by a width less than a mean free path of a gas molecule being ionized;

a characterization unit coupled to said ionizing device, for receiving and characterizing ionized molecules from said ionizing device; and

wherein said characterization unit and said ionizing device are configured to transversally disperse ions at substantially ambient pressure.

98. A method for ionizing and dispersing a sample of molecules comprising the steps of:

providing an ionizing device having one or more pairs of electrodes having a spacing less than the mean free path of the molecule being ionized;

applying a voltage across the pair of electrodes to generate a field to ionize substantially all molecules passing between the pair of electrodes;

ionizing molecules passing through the electric field generated by the pair of electrodes; and

accelerating the ionized molecules using a later accelerator and substantially without a pump.

99. A method of claim 98 further comprising the step of characterizing the accelerated ionized molecules.